The Quarterly Journal of Science, Literature and the Arts, July-December, 1827

by Various

ASTRONOMICAL AND NAUTICAL COLLECTIONS.

i. Elementary View of the UNDULATORY Theory of LIGHT. By Mr. FRESNEL. [◊] [Continued from the last Number.]

I SHALL not undertake to explain here in detail the reasons and the calculations which lead to the general formulas that I have employed to determine the position of the fringes and the intensity of the inflected rays: but I think it right to give at least a distinct idea of the principles on which this theory rests, and particularly of the principle of interference, which explains the mutual action of the rays of light on each other. The name of interference was given by Dr. YOUNG to the law which he discovered, and of which he has made so many ingenious applications.

This singular phenomenon, so difficult to be satisfactorily explained in the system of emanation, is on the contrary so natural a consequence of the theory of undulation, that it might have been predicted from a general consideration of the principles of that theory. Every body must have observed, in throwing stones into a pond, that, when two groups of waves cross each other on its surface, there are points at which the water remains immoveable, when the two systems are nearly of the same magnitude, while there are other places in which the force of the waves is augmented by their concurrence. The reason of this is easily understood. The undulatory motion of the surface of the water consists of vertical motions, which alternately raise and depress the particles of the fluid. Now, in consequence of the intersection of the waves, it happens, that at certain points of their meeting, one of the two waves has an ascending motion belonging to it, while the other tends at the same instant to depress the surface of the liquid: consequently, when the two opposite impulses are equal, it can neither be actuated by one nor the other, but must remain at rest. On the contrary, at the points in which the motions agree in their direction, and conspire with each other, the liquid, urged in the same direction [p114] by each of the forces, is raised or depressed with a velocity equal to the sum of the effects of the two separate impulses, or to the double of either of them taken singly, since they are now supposed to be equal. Between these points of perfect agreement and complete opposition, which exhibit, one the total absence of motion, the other the maximum of oscillation, there are an infinity of intermediate points, at which the alternate motion takes place with more or less of energy, accordingly as they approach more or less to the places of perfect agreement, or of complete opposition of the two systems of motion which are thus combined, or superinduced on each other.

The waves which are propagated in the interior of an elastic fluid, though very different in their nature from those of a liquid like water, produce mechanical effects by their interference, which are exactly of the same kind, since they consist in alternate oscillatory motions of the particles of the fluid. In fact, it is sufficient that these motions should be oscillatory, that is, that the particles should be carried by them alternately in opposite directions, in order that the effects of one series of waves may be destroyed by those of another series of equal intensity; for, provided that the difference of the route of the two groups of waves [derived from the same origin] be such, that for each point of the fluid the motions in one direction, belonging to the first series, correspond to the motions, belonging to the second, in the opposite direction, they must perfectly neutralise each other, if their intensity is equal: and the particles of the fluid must remain in repose. This result will always hold good, whatever may happen to be the direction of the oscillatory motion, with regard to that in which the undulations are propagated; provided that the direction of the oscillatory motion be the same in the two series to be combined. In the waves which are formed on the surface of a liquid, for example, the direction of the oscillation is [principally] vertical, while the waves are propagated horizontally, and consequently in a direction perpendicular to the former; in the undulations of sound, on the contrary, the oscillatory motion is parallel to the direction of the propagation of the sound, [or rather is [p115] identical with it]; and these undulations, as well as the waves of water, are subject to the laws of interference.

The undulations formed in the interior of a fluid have here been mentioned in a general manner: in order to form a distinct idea of this mode of propagation, it must be remarked, that when the fluid has the same density and the same elasticity in every direction, the agitation produced in any point must be propagated on all sides with the same velocity: for this velocity of propagation, which must not be confounded with the absolute velocity of the particles, depends only on the density and elasticity of the fluid. It follows thence that all the points, agitated at the same instant in a similar manner, must be found in a spherical surface, having for its centre the point which is the origin of the agitation: so that these undulations are spherical, while the waves, which are seen on the surface of a liquid, are simply circular.

We give the name of rays to the right lines drawn from the centre of agitation to the different points of this spherical surface; and these rays are the directions in which the motion is propagated. This is the meaning of the term sonorous rays in acustics, and of luminous rays or rays of light in the system which attributes the phenomena of light to the vibrations of a universal fluid, to which the name of ether has been given.

The nature of the different elementary motions, of which each wave is composed, depends on the nature of the different motions which constitute the primitive agitation. The simplest hypothesis that can be entertained concerning the formation of the luminous undulations, is, that the small oscillations of the particles of the bodies, which produce them, are analogous to those of a pendulum removed but little from its point of rest; for we must conceive the particles of bodies, not as immoveably fixed in the positions which they occupy, but as suspended by forces which form an equilibrium in all directions. Now, whatever the nature of such forces may be, as long as the displacement of the particles is but small in proportion to the extent of their sphere of action, the accelerating force which tends to restore them to their natural position, and which thus causes them to oscillate on each side of it, may always, without sensible error, be considered as proportional [p116] to the magnitude of that displacement: so that the law of their motion must be the same as that of the motion of the pendulum, and of all small oscillations in general. This hypothesis, which is suggested by the analogy with other natural phenomena, and which is the simplest that can be formed respecting the vibrations of the luminous particles, may be considered as experimentally confirmed by the observation, that the optical properties of light are all independent of any circumstances which cause the greatest difference in the intensity of the vibrations: so that the law of their motion must be presumed to be the same for the greatest as for the smallest.

It follows from this hypothesis respecting the small oscillations, that the velocity of the vibrating particle at each instant is proportional to the sine of an arc, representing the time elapsed from the beginning of the motion, taking the circumference for the whole time required for the return of the particle to the same point, that is, the time occupied by two oscillations, the one forwards and the other backwards. Such is the law according to which I have calculated the formulas which serve to determine the effect of any number of systems of waves of which the intensities and the relative positions are given. These formulas will be found in the Annals of Chemistry, vol. xi., page 254: [they may be applied with security to the phenomena there considered, though the perfect accuracy of the hypothesis in all possible cases may be questioned, upon the grounds of the microscopical observations on the motions of vibrating chords, published by Dr. Young in the Philosophical Transactions for 1800. TR.] Without entering into the details of the calculations, I think it necessary to show in what manner the nature of the undulation depends on the kind of motion of the vibrating particles.

Let us suppose, in the fluid, a little solid plane which is removed from its primitive position, towards which it is urged by a force proportional to the distance. At the beginning of its motion, the accelerative force produces in it an infinitely small velocity only; but its action continuing, the effects become accumulated, and the velocity of the solid plane goes on continually to increase, until the moment of its arrival at [p117] the position of equilibrium, in which it would remain, but for the velocity which it has acquired; and it is by this velocity only, that it is carried beyond the point of equilibrium. The same force which tends towards this point, and which now begins to act in a contrary direction, continually diminishes the velocity, until it is completely annihilated; and then the force continuing its action produces a velocity in the contrary direction, which brings the plane back to its place of equilibrium. This velocity again is very small at the commencement of the return of the particle, or plane, and increases by the same degrees as it had before diminished, until the instant of the arrival of the particle at the neutral point, which it passes with the velocity previously acquired: but when it has passed this point, the motion is diminished more and more by the effect of the force tending towards it, and its velocity is reduced to nothing when it arrives at the place of the commencement of the motion. It then recommences, at similar periods, the series of motions which have been described, and would continue to oscillate for ever, but for the effect of the resistance of the surrounding fluid, the inertia of which continually diminishes the amplitude of its oscillations, and finally extinguishes them at the end of a longer or shorter time, according to circumstances. [It must not be inferred from this explanation, that the particles of a fluid transmitting an undulation have any tendency to vibrate for ever: on the contrary it has been admitted by the best writers on the theory of sound, that all the motions which constitute it, as considered in a fluid, are completely transitory in their nature, and have no disposition to be repeated after having been once transmitted to a remoter part of the fluid. TR.]

Let us now consider in what manner the fluid is agitated by these oscillations of the solid plane. The stratum immediately in contact with it, being urged by the plane, receives from it at each instant the velocity of its motion, and communicates it to the neighbouring stratum, which it forces forwards in its turn, and from which the motion is communicated successively to the other strata of the fluid; but this transmission of the motion is not instantaneous, and it is only at the end of a certain time that it arrives at a determinate [p118] distance from the centre of agitation. This time is the shorter, as the fluid is less dense, and more elastic; that is, composed of particles which possess a greater repulsive force. This being granted, let us assume, in order to facilitate the explanation, the moment when the moveable plane is returned to the initial situation, after having performed two complete oscillations in opposite directions: at this moment, the nascent velocity, which it had at first, is transmitted to a stratum of the fluid removed from the centre of agitation by a distance which we may represent by d. Immediately afterwards, the velocity of the moveable plane, which has a little augmented, has been communicated to the stratum in contact with it: “hence it has passed successively through all the following strata;” and at the moment when the first agitation arrives at the stratum of which the distance is d, the second has arrived at the stratum immediately before it. Continuing thus to divide, in our imagination, the duration of the two oscillations of the moveable plane into an infinity of small intervals of time, and the fluid comprehended in the length d, into an equal number of infinitely thin strata, it is easy to perceive, by the same reasoning, that the different velocities of the moveable plane, at each of these instants, are now distributed among the corresponding strata; and that thus, for example, the velocity which the plane possessed at the middle of the first oscillations in the direction of the motion, must have arrived, at the instant in question, at the distance 34 d: so that it is the stratum at this distance which possesses at the moment the greatest direct velocity; and in the same manner when the plane arrived at the limit of its first direct oscillation, its velocity was extinguished, and the same absence of motion will be found at the distance 12 d.

It is always supposed, that the oscillations of the plane are so minute in comparison with the length d, that their extent may be neglected in this calculation: and this hypothesis is actually consistent with the fact, since there is every reason to suppose that the excursions of the incandescent particles are very small in comparison with the extent of an undulation, which, though an extremely minute space, is still an appreciable quantity, and may be actually measured. Besides, [p119] even if the amplitude of these oscillations were not in the first instance so wholly inconsiderable, it would be sufficient to consider an undulation at a greater distance from the centre of agitation, in order that their extent might be diminished in any required proportion.

In the second, or retrograde oscillation, the plane, returning through the same space, must communicate to the stratum of fluid in contact with it, and to the rest in succession, a motion in a direction contrary to that of the first oscillation; for when the plane recedes, the stratum in contact with it, urged against the plane by the elasticity or the expansive force of the fluid, necessarily follows it, and fills up the vacuum which its retrograde motion tends to produce. For the same reason, the second stratum is urged against the first, the third against the second, and so forth. It is thus that the retrograde motion is communicated, step by step, to the most distant strata: its propagation is effected according to the same law that governs the direct motion; the only difference is in the direction of the motions, or, in the language of mathematics, in the sign of the velocities which are imparted to the molecules of the fluid. We see then that the different velocities which have existed in the solid plane, during its second oscillation, must exist at the moment which we are considering, in the different strata comprehended in the other half of d, but with contrary signs. Thus the velocity, for example, which the plane had in the middle of the second oscillation, which is its maximum of retrograde velocity, must now be found in the fluid stratum situated at the distance 14 d from the centre of agitation, while the maximum of direct velocity is found, at the same instant, in the stratum which is at the distance 34 d from the centre of agitation.

The extent of the fluid, agitated by the two opposite oscillations of the solid plane, is what we call the breadth of an entire undulation, and we may consequently give the name of semiundulation to each of the parts actuated by the opposite undulations; the whole constituting a complete oscillation, since it comprehends the return of the vibrating plane to the initial situation. It is obvious, that the two semiundulations, which compose the complete undulation, exhibit, in [p120] the fluid strata which they contain, velocities absolutely equal in magnitude, but with contrary signs, that is to say, carrying the particles of the fluid in opposite directions. These velocities are the greatest in the middle of each of the semiundulations, and decrease gradually towards their extremities, where they entirely vanish: so that the points of rest, and of the greatest velocities positive and negative, are separated from each other by intervals of one fourth of an undulation.

The length of an undulation, d, depends on two things: first, on the promptitude with which the motion is propagated in the fluid; and secondly, the duration of the complete oscillation of the vibrating plane; for the longer this duration, and the more rapid the propagation of the motion, the greater will be the distance to which the first agitation has been extended at the instant of the return of the solid plane to its initial situation. If the oscillations are all performed in the same medium, the velocity of propagation remaining the same, the length of the undulations will be simply proportional to the duration of the oscillations of the vibrating particles from which they originate. As long as the vibrating particles continue to be subjected to the same forces, it follows from the principles of mechanics that each of their minute oscillations will occupy the same time, whatever their extent may be; so that the corresponding undulations of the fluid will continue to be of the same length; they will only differ from each other in the greater or less extent of the elementary vibrations of the particles, which will be proportional to the extent of the luminous particles; for it appears from what has already been stated, that each stratum of the fluid repeats exactly all the motions of the vibrating particle. The greater or less amplitude of the oscillations of the strata of the fluid determines the degree of absolute velocity with which they move, and consequently the energy, but not the nature of the sensation which they excite, which must depend, according to every analogy, upon the duration of the oscillations. It is thus that the nature of the sounds, transmitted by the air to our ears, depends entirely on the duration of each of the oscillations executed by the air, or by the sonorous [p121] body which puts it in motion; and that the greater or less amplitude or energy of the oscillations only augments or diminishes the intensity of the sound, without changing its nature, that is, its tone, or pitch.

The intensity of the light must depend then on the intensity of the vibrations of the ether; and its nature, that is to say, the sensation of colour that it produces, will depend on the duration of each oscillation, or on the length of the undulation, the one of these being proportional to the other. [We find, however, nothing in light of the same colour that is at all analogous to the different register, quality, or timbre of a sound; by which, for instance, the sound of a violin differs from that of a flute in unison with it: the subordinate, or harmonic tones of the sound having nothing in light to correspond with them. TR.]

The duration of the elementary oscillation remaining the same, the absolute velocity of the ethereal particles, at the corresponding periods of the oscillatory motions, is, as we have seen, proportional to its extent. It is the square of this velocity, multiplied by the density of the fluid, that represents what is called the living force in mechanics, or otherwise the energy or impetus of the particles, which is to be taken as the measure of the sensation produced, or of the intensity of the light: thus, for example, if in the same medium, the amplitude of the oscillation is doubled, the absolute velocities will also be doubled, and the living force, or the intensity of the light, will be quadrupled.

We must, however, take care not to confound this absolute velocity of the particles of the fluid with the velocity of the propagation of the agitation. The first varies according to the amplitude of the oscillations; the second, which is nothing but the promptitude with which the motion is communicated from one stratum to the other, is independent of the intensity of the vibrations. It is for this reason, that a weak sound is transmitted by the air with the same velocity as a stronger one; and that the least intense light is propagated with the same rapidity as the brightest. When we speak of the velocity of light, we always speak of the velocity of its propagation. Thus, when we say that light passes through 200 thousand [p122] miles in a second, we do not mean, according to the undulatory system, that such is the absolute velocity of the ethereal particles; but that the motion communicated to the ether employs only a second to pass to a stratum at the distance of 200 thousand miles from its origin.

In proportion as the undulation becomes more distant from the centre of agitation, the motion, spreading over a greater distance, must be weakened in every part of the wave. It is shown by calculation, that the amplitude of the oscillatory motion, or the absolute velocity of the particles concerned in it, is inversely proportional to the distance from the centre of agitation. Consequently, the square of this velocity is inversely proportional to the square of the distance, and the intensity of the light must be inversely as the square of the distance from the luminous point. It must be remarked, that, for the same reasons, the sum of the living forces of the whole undulation remains unaltered; for, on one side the length of the undulation d, which may also be called its thickness, is invariable, and its extent of surface augmenting in proportion to the square of the distance from the centre, the quantity, or mass of the fluid agitated, is proportional to the same square: and since the squares of the absolute velocities are diminished in the same proportion as the masses have augmented, it follows that the sum of the products of the masses by the squares of the velocities, that is to say, the sum of the living forces, remains unaltered. It is a general principle of the motion of elastic fluids, that however the motion may be extended or subdivided, the total sum of the living forces remains constant; and this is the principal reason why the living force must be considered as the measure of light, of which the total quantity always remains very nearly the same, at least as long as it continues to pass through perfectly transparent mediums.

It may be remarked, that black substances, and even the most brilliant metallic surfaces, by no means reflect the whole of the light which falls on them; bodies which are imperfectly transparent, and even the most transparent, when of great thickness, absorb also, to use a common expression, a considerable portion of the light that is passing through [p123] them: but it must not be inferred that the principle of living forces is inapplicable to these phenomena; it follows, on the contrary, from the most probable idea that can be formed of the mechanical constitution of bodies, that the sum of the living force must remain always the same, as long as the accelerating forces tending to bring the particles to their natural positions remain unchanged, and that the quantity of living force which disappears in the state of light, instead of being annihilated, is reproduced in the form of heat.

In order to obtain a correct idea of the manner in which the oscillation of a small solid body occasions undulations in an elastic fluid, it has been only necessary to consider a complete oscillation of the solid plane, which produces an entire undulation. If we suppose the oscillations of the plane to be continually repeated, we shall have a series of undulations instead of a single one: and they will follow each other without intermission, provided that the vibrations of the particle first agitated have been regular. Such a series of regular and uninterrupted luminous motions I call a system of undulations.

It is natural to suppose, on account of the prodigious rapidity of the vibrations of light, that the luminous particles may perform a great number of regular oscillations in each of the different mechanical situations in which they are placed during the combustion or the incandescence of the luminous body, although these circumstances may still succeed each other in extremely short periods; for the millionth part of a second is sufficient to exhibit, for example, 545 millions of undulations of yellow light; so that the mechanical disturbances, which derange the regular succession of the vibrations of the luminous particles, or which even change their nature, might be repeated a million times in a second without preventing the regular succession of more than 500 millions of consecutive undulations in each state of the particle. We shall soon have occasion to apply this observation to the determination of the circumstances in which the interference of luminous waves is capable of producing sensible effects.

We have seen that each undulation produced by an oscillatory motion was composed of two semiundulations, which [p124] occasioned in the particles of the fluids velocities exactly equal in their intensity, though opposite in the direction of the motions. Let us at first suppose that two whole undulations, moving in the same line and in the same direction, differ half an undulation in their progress: they will then be superinduced on each other through one half of their length, or of their breadth, as we should say in speaking of the waves of a liquid: but I here use in preference the term length as applied to the interval between the two points which are similarly affected by the motions of two consecutive undulations. In the supposed case of the coincidence of one half of each of the undulations, the interference will only take place with respect to the parts so coinciding: that is, to the latter half of the first undulation, and the preceding half of the second: and if these two semiundulations are of equal intensity, since they tend to give, to the same points of the ether, impulses directly opposite, they will wholly neutralise each other, and the motion will be destroyed in this part of the fluid, while it will subsist without alteration in the two other halves of the undulations. In such a case, therefore, half of the motion only would be destroyed.

If now we suppose that each of these undulations, differing in their progress by half the whole length of each, is preceded and followed by a great number of other similar undulations; then, instead of the interference of two detached undulations, we must consider the interference of two systems of waves, which may be supposed equal in their number and their intensity. Since, by the hypothesis, they differ half an undulation in their progress, the semiundulations of the one, which tend to cause in the particles of ether a motion in one direction, coincide with the semiundulations of the other, which urge them in the opposite direction, and these two forces hold each other in equilibrium, so that the motion is wholly destroyed in the whole extent of these two systems of waves, except the two extreme semiundulations, which escape from the interference. But these semiundulations will always constitute a very small part of the whole series to be considered.

This reasoning is obviously applicable to such systems only [p125] as are composed of undulations of the same length; for if the waves were longer one than the other, however small their difference might be, it would happen at last that their relative position would not be the same throughout the extent of the groups; and while the first destroyed each other almost completely, the following ones would be less in opposition, and would ultimately agree completely with each other: hence there would arise a succession of weak and strong vibrations analogous to the beatings which are produced by the coincidence of two sounds differing but little from each other in their tone; but these alternations of weaker and stronger light, succeeding each other with prodigious rapidity, would produce in the eye a continuous sensation only.

It is very probable that the impulse of a single luminous semiundulation, or even of an entire undulation, would be too weak to agitate the particles of the optic nerve, as we find that a single undulation of sound is incapable of causing motion in a body susceptible of a sympathetic vibration. It is the succession of the impulse, which, by the accumulation of the single effects, at last causes the sonorous body to oscillate in a sensible manner; in the same manner as the regular succession of the single efforts of a ringer is at last capable of raising the heaviest church bell into full swing. Applying this mechanical idea to vision, supported as it is by so many analogies, we may easily conceive that it is impossible for the two remaining semiundulations, which have been mentioned, to produce any sensible effect on the retina; and that the result of such a combination of the two systems must be the production of total darkness.

If again we suppose the second system of undulations to be again retarded half an undulation more, so as to make the difference of the progress an entire undulation, the coincidence in the motions of the two groups will be again restored, and the velocities of oscillation will conspire and be augmented in the points of superposition; the intensity of the light being then at its maximum.

Adding another semiundulation to the difference in the progress of the two systems, so as to make it an interval and [p126] a half, it is obvious that the semiundulations, superinduced on each other, will now possess opposite qualities, as in the case of the half interval first supposed: and that all the undulations must in this manner be neutralised, except the extreme three semiundulations on each side, which will be free from interference. Thus almost the whole of the motion will again be destroyed, and the combination of the two pencils of light must produce darkness, as in the case first considered.

Continuing to increase the supposed difference by the length of a semiundulation at each step, we shall have alternately complete darkness and a maximum of light, accordingly as the difference amounts to an odd or an even number of semiundulations: that is, supposing always that the systems of undulations are of equal intensity: for if the one series were less vivid than the other, they would be incapable of destroying them altogether: the velocities of the one series would be subtracted from those of the other, since they would tend to move the particles of the ether in contrary directions, but the remainders would still constitute light, though feebler than that of the strongest single pencil. Thus the second pencil would still occasion a diminution of the light: but the diminution would be the less sensible as the pencil is supposed to be weaker.

Such are the consequences of the principle of the interference of undulations, which agree perfectly, as we have seen, with the law of the mutual influence of the luminous rays which is deduced from experiment: for the results are expressed precisely in the same words, if we give the name of length of undulation to the difference of routes which had been represented by the symbol d. Admitting, therefore, as there is every reason to believe, that light consists in the undulations of a subtile fluid, the period d, after which the same effects of interference are repeated, must be the length of an undulation.

It appears from the table already given for the seven principal kinds of coloured rays, that this period d, or the length of the undulation, varies greatly, according to the [p127] colour of the light, and that for the extreme red rays, for example, it is [more than] half as great again as for the violet rays situated at the other extremity of the spectrum.

It may easily be imagined that the number of different undulations is not limited to the seven principal ones which are indicated in the table, and that there must be a multitude of intermediate magnitudes, and others beyond the red and the violet rays: for the ponderable particles, of which the oscillations give rise to them, must be subjected to forces that are infinitely varied, in the combustion or the incandescence of the bodies which excite the motions of the ether: and it is on the energy of these forces that the duration of each oscillation depends, and consequently the length of the undulation produced by it. It is found that all the undulations comprehended [in the air] between the lengths .0000167 E.I. and .0000244, are visible; that is, are capable of exciting vibrations in the optic nerve: the rest are only sensible by their heat, or by the chemical effects which they produce.

It has been remarked, that when two systems of waves differ half an undulation in their progress, two of the semiundulations must escape from interference; that six must be exempt when the difference amounts to three semiundulations; and that, in general, the number of undulations exempt from interference is equal to the number of lengths of a semiundulation separating the corresponding points of the two systems. While this number is very small in proportion to that of the waves contained in each system, the motion must be nearly destroyed, as in the case of the exemption of a single undulation. But it may be imagined that, as we increase the difference of the progress of the two pencils, the undulations exempted from interference may become a material portion of each group, and that it may finally become so great as to separate the groups entirely from each other; and in this case the phenomena of interference would no longer be observable. If, for example, the groups of undulations consisted but of a thousand each, a difference of one-twentieth of an inch in their routes would be much more than sufficient to prevent the interference of the rays of all kinds. [p128]

But there is another much more powerful reason which prevents our perceiving the effects of the mutual influence of the systems of waves when the difference of their routes is considerable; which is the impossibility of rendering the light sufficiently homogeneous: for the most simple light that we can obtain consists still of an infinity of heterogeneous rays, which have not exactly the same length of undulation; and however slight the difference may be, when it is repeated a great number of times, it produces of necessity, as we have already seen, an opposition between the modes of interference of the various rays, which then compensates for the weakening of some by the strengthening of others; [while the shades of colour are not sufficiently distinct to allow the eye to remark the difference.] This is without doubt the principal reason why the effects of the mutual interference of the rays of light become insensible when the difference of the routes is very considerable, so as to amount to 50 or 60 times the length of an undulation.

It has already been laid down as one of the conditions necessary for the appearance of the phenomena of interference, that the rays which are combined should have issued at first from a common source: and it is easy to account for the necessity of this condition by the theory which has now been explained.

Every system of waves, which meets another, always exercises on it the same influence when their relative positions are the same, whether it originates from the same source or from different sources; for it is clear that the reasons, by which their mutual influence has been explained, would be equally applicable to either case. But it is not sufficient that this influence should exist, in order that it may become sensible to our eyes: and for this purpose the effect must have a certain degree of permanence. Now this cannot happen when the two systems of waves which interfere are derived from separate sources. For it is obvious that the particles of luminous bodies, of which the vibrations agitate the ether, and produce light, must be liable to very frequent disturbances in their oscillations, in consequence of the rapid changes which are taking place around them, which may [p129] nevertheless be perfectly reconciled, as we have seen, with the regular continuance of a great number of oscillations in each of the series separated by these perturbations. This being admitted, it is impossible to suppose that these perturbations should take place simultaneously and in the same manner in the vibrations of separate and independent particles; so that it will happen, for example, that the motions of the one will be retarded by an entire semioscillation, while those of the other will be continued without interruption, or will be retarded by a complete oscillation, a change which will completely invert the whole effects of the interference of the two systems of undulations which originate from them; since if they had agreed on the first supposition, they would totally disagree on the second. Now these opposite effects, succeeding each other with extreme rapidity, will produce in the eye a continuous sensation only, which will be a mean between the more or less lively sensations that they excite, and will remain constant, whatever may be the difference of the routes described.

But the case is different when the two luminous pencils originate from a common source: for then the two systems of waves, having originated from the same centre of vibration, undergoing these perturbations in the same manner and at the same instant, undergo no changes in their relative positions: so that if they disagreed in the first instance at any given point, they would continue to disagree at all other times; and if their motions cooperated at first, they would continue to agree as long as the centre of vibration continued to be luminous: so that in this case, the effects must remain constant, and must therefore be sensible to the eye. This is therefore a general principle, applicable to all the effects produced by luminous undulations; that in order to become sensible, they must be permanent.

We have hitherto supposed that the two systems of waves were moving exactly in the same direction, and that consequently their elementary motions, to be combined with each other, were precisely limited to one single line: this is the simplest case of interference, and the only one in which the one motion can be completely destroyed by the other: [p130] for in order that this effect may be produced, not only the two forces must be equal and in contrary directions, but they must also act in the same right line, or be directly opposed to each other.

The phenomenon of coloured rings, and that of the colours developed by polarised light in crystallised plates, present a particular case of interference, in which the undulations are exactly parallel. But in the phenomena of diffraction, or in the experiment with the two mirrors, which has been already described, the rays which interfere always form sensible though very small angles with each other. In these cases the impulses to be combined with each other at the same points, as belonging to the two systems of undulations, will also act in directions forming sensible angles with each other: but on account of the smallness of these angles, the result of the two impulses is almost exactly equal to their sum, when the impulses act in the same direction, and to their difference, when they are in contrary directions. Thus, in the points of agreement or disagreement, the intensity of the light will be the same as if the directions agreed more perfectly; at least the nicest eye will not be able to discover any difference in them. But although, with respect to the intensity of the light, this case of interference resembles that which has already been considered, there are other differences which modify the phenomenon very greatly, both with respect to its general form, and to the circumstances necessary for producing it.

We may take, as a convenient example, the case of diverging rays originating from the same luminous point, and reflected by two mirrors slightly inclined to each other, so as to produce two pencils meeting each other in a sensible angle: the two systems of waves will then meet each other with a slight inclination; and it follows from this obliquity, that if a semiundulation of the first system coincides perfectly in one point with a semiundulation of the second, urging the fluid in the same direction, it must separate from it to the right and left of the point of intersection, and must coincide, a little further off, on one side with the preceding semiundulation which is in a contrary direction, [p131] and on the other side with the following semiundulation, and then be separated from this again, and at a distance twice as great as the first, must coincide with the second semiundulation before and behind it, of which the actions will coincide with its own: whence there will arise, on the surface of this undulation, a series of lines, at equal distances from each other, in which the motion is destroyed and doubled alternately by the action of the second series. Thus if we receive this luminous undulation on a white card, we shall observe on it a series of dark and bright stripes, if the light employed is homogeneous; or coloured fringes of different tints, if we employ white light for the experiment.

This will be more easily understood by the inspection of a figure, which represents a section of the two mirrors and of the reflected undulations, formed by a plane drawn from the luminous point perpendicularly to the mirrors represented by DE and DF. The luminous point is supposed to be S, and A and B are the geometrical positions of its two images, which are determined by the perpendiculars SA and SB falling from S on the mirrors, taking in them PA = SP [p132] and QB = SQ. The points A and B, thus found, are the centres of divergence of the rays reflected from the respective mirrors, according to the well known law of reflection. Thus, in order to have the direction of the ray reflected at any point G of the mirror DF, for example, it is sufficient to draw a right line through B and G, which will be the direction of the reflected ray. Now it must be remarked, that, according to the construction by which the position of B is found, the distances BG and SG will be equal, and thus the whole route of the ray coming from S and arriving at b, is the same as if it had come from B. This geometrical truth being equally applicable to all the rays reflected by the same mirror, it is obvious that they will arrive at the same instant at all the points of the circumference n′bm, described on the point B as a centre, with a radius equal to Bb; consequently this surface will represent the surface of the reflected undulation when it arrives at b, or, more correctly speaking, its intersection with the plane of the figure: the surface of the undulation being understood as relating to the points which are similarly agitated at the same instant: the points being all, at the commencement of the whole oscillation, for example, or at the middle or the end, completely at rest; and in the middle of each semioscillation, possessed of the maximum of velocity.

In order to represent the two systems of reflected undulations, there are drawn, with the points A and B for their centres, two different series of equidistant arcs, separated from each other by an interval which is supposed equal to the length of a semiundulation. In order to distinguish the motions in opposite directions, the arcs on which the motions of the ethereal particles are supposed to be direct, are represented by full lines, and the maximum of the retrograde motions are indicated by dotted lines. It follows that the intersections of the dotted lines with the full lines are points of complete discordance, and of course show the middle of the dark stripes; and, on the contrary, the intersections of similar arcs show the points of perfect agreement, or the middle of the bright stripes. The intersections of the arcs of the same kind are joined by the dotted lines b′p′, br, b′p′, and those of arcs of [p133] different kinds by the full lines n′o′, no, no, n′o′: these latter representing the successive positions or the trajectories of the middle points of the dark stripes, and the former the trajectories of the bright bands.

It has been necessary to magnify very greatly in this figure the real length of the luminous undulations, and to exaggerate the mutual inclination of the two mirrors, so that we must not expect an exact representation of the phenomenon, but merely a mode of illustrating the distribution of the interferences, in undulations which cross each other with a slight inclination.

It is easy to deduce from geometrical considerations, that the length of these fringes is in the inverse ratio of the magnitude of the angle made by the two pencils which interfere, and that the interval, comprehended between the middle points of two consecutive dark or bright bands, is as much greater than the length of the undulation, as the radius is greater than the sine of the angle of intersection.

In fact the triangle bni, formed by the right line bi, and the two circular arcs ni and nb, may be considered as rectilinear and isosceles, on account of the smallness of the arcs; and the sine of the angle bni, considered as very small, may be called ibbn: so that bn being the radius, ib will represent the sine of the angle bni, which has its legs perpendicular to those of the angle AbB: consequently, these angles being equal, one of them may be substituted for the other; and representing by i the angle AbB, formed by the reflected rays, we have bn = ibsin i; consequently nn, which is twice bn, will be equal to 2ibsin i. But nn is the distance between the middle points of two consecutive dark stripes, and is the distance which has been called the breadth of a fringe; and ib being the breadth of a semiundulation, according to the construction of the figure, 2ib will be that of a whole undulation; consequently the breadth of a fringe may be said to be equal to the length of an undulation divided by the [numerical] sine of the angle made by the reflected rays [p134] with each other, which is also the angle under which the interval AB would appear to an eye placed at b. We find another equivalent formula, by remarking that the two triangles, bni and AbB, are similar, whence we have the proportion bn: bi = Ab : AB, and bn = bi × AbAB, or 2bn = 2bi × AbAB: which implies that we may find the numerical breadth of a fringe by multiplying the length of an undulation by the distance of the images A and B from the plane on which the fringes are measured, and dividing the product by the distance of the two images.

It is sufficient to inspect the figure, in order to be convinced of the necessity of having the two mirrors nearly in the same plane, if we wish to obtain fringes of tolerably large dimensions; for in the little triangle bni, the side bi, which represents the length of a semiundulation, being little more than the hundred thousandth of an inch for the yellow rays, for example, the side bn, which measures the half breadth of a fringe, can only become sensible when bn is very little inclined to in, so that their intersection may be remote from ib; and the inclination of bn to in depends on the distance AB, which is the measure of the inclination of the mirrors.

If A and B, instead of being the images of the luminous point, were the projections of two very fine slits cut in a screen RN, through which the rays of light were admitted from a luminous point placed behind the screen in the continuation of the line bDC, the two paths described between the point and the slits A and B being equal, it would be sufficient to compute the paths described by the rays, beginning from A and B, in order to have the differences of their lengths; and it is obvious in this case, that the calculations which we have been making of the breadth of the fringes, produced by the two mirrors, would remain equally applicable, at least as long as each slit remained narrow enough to be considered as a single centre of undulation, relatively to the inflected rays which it transmits. It may therefore be said that the breadth of the fringes, produced by two very fine slits, is equal to the length of an undulation supposed [p135] to be multiplied by the interval between the two slits, and divided by the distance of the screen from the wires of the micrometer employed for measuring the fringes.

This formula is also applicable to the dark and bright stripes which are observed in the shadow of a narrow substance, substituting the breadth of this substance for the interval which separates the two slits, as long as the stripes are far enough from the edges of the shadow: for when they approach very near to the edges, it is shown, both by theory and by experiment, that this calculation does not represent the facts with sufficient accuracy; and it is not perfectly correct in all cases, either for the fringes within the shadow, or for those of the two slits, but only for the fringes produced by the mirrors, which exhibit the simplest case of the interference of rays slightly inclined to each other. In order to obtain from the theory, a rigorous determination of the situation of the dark and light stripes in the two former cases, it is not sufficient to calculate the effect of two systems of undulations, but those of an infinite number of similar groups must be combined, according to a principle which will shortly be explained, in treating of the general theory of diffraction.

ii. Rule for the Correction of a LUNAR OBSERVATION. By Mr. WILLIAM WISEMAN, of Hull. [◊]

RULE.

ADD together the reserved logarithm (found as directed, page 111 and 112 of the Appendix to the third edition of the Requisite Tables) the log. sines of half the sum, and half the difference of the apparent distance, and difference of apparent altitudes, and 0.3010300, the log. of 2. Then, to the natural number corresponding to the sum of these four logarithms, add the natural verse sine of the difference of true altitudes, and the sum will be the natural verse sine of the true distance.

Or, having obtained the natural number, as directed above, subtract it from the natural cosine of the difference of the true altitudes, and the remainder will be the natural cosine of the true distance. [p136]

EXAMPLE.

(From page 112, Appendix to Requisite Tables.)

Reserved log. from Tables (Req.) 9th and 11th		9.9938860
Log. sin. 43° 23′ 5″ =12sum of app. dist. and diff. app. altitudes		9.8368895
Log. sin. 6° 45′ 36″ =12diff. ditto ditto		9.0708157
Log. of 2		0.3010300
Nat. num. to sum of 4 logarithms	.1594488	9.2026212
Nat. vers. 37° 13′ 12″ = diff. true altitudes	.2036812
Nat. vers. 50° 26′ 28″ = true distance	.3631300
Or, Nat. cos. 37° 13′ 12″ = diff. true altitudes		.7963188
Nat. number found above		.1594488
Nat. cosin. 50° 26′ 28″ = true distance		.6368700

DEMONSTRATION OF THE RULE.

Let M′, S′, D′, d′ and M, S, D, d, respectively denote the true and apparent altitudes, distances, and differences of true and apparent altitudes of the moon and sun (or a star); then will the theorem answering to the above rule be expressed by vers. D′ = 2 cos M′ cos S′cos M cos S × sin12(D + d) × sin12(D−d) + vers. d′.

By Bonnycastle’s Trig. p. 175, the cosine of the angle contained by the co-altitudes is cos D−sin M sin Scos M cos S = cos D′−sin M′ sin S′cos M′ cos S′; consequently the verse sine of the same angle = 1−cos D−sin M sin Scos M cos S = 1−cos D′−sin M′ sin Scos M′ cos S′; that is, cos M cos S+sin M sin S−cos Dcos M cos S = cos M′ cos S′+sin M′ sin S′−cos D′cos M′ cos S′.

Substituting cos d and cos d′ for cos M cos S + sin M sin S and cos M′ cos S′ + sin M′ sin S′. (Bon. Trig. p. 282), we have cos d−cos Dcos M cos S = cos d′−cos D′cos M′ cos S′; whence cos D′ = cos d′−cos M′ cos S′cos M cos S × (cos d−cos D); or, which is the same, cos D′ = cos d′−cos M′ cos S′cos M cos S × (vers D−vers d); or, (Bon. Trig. p. 286.) [p137] cos D′ = cos d′−cos M′ cos S′cos M cos S × (2 sin²12D − 2 sin²12d); that is, cos D′ = cos d′−2 cos M′ cos S′cos M cos S × sin12(D + d) × sin12(D−d); whence also vers D′ = vers d′ + 2 cos M′ cos S′cos M cos S × sin 12(D + d) × sin12(D−d).

It may be observed, that Requisite Tables 9–11, answer logarithmically to cos M′ cos S′cos M cos S; and the verse sines, and the cosines can be very readily taken out of the tables in the Appendix. Also no ambiguity can arise from the application of the rule before given: for all the arcs concerned in the operation will always be (each of them) less than a quadrant, except the resulting true distance, which cannot cause any ambiguity; and the verse sines are given in the Appendix, to 126°.

EXAMPLE.

(Example 2nd, p. 39, Requisite Tables.)

Reserved log. from Tables 9 and 10		9.995307
Log. sin 62° 45′ 56″ =12sum app. dis. and diff. app. alts.		9.948971
Log. sin 40° 43′ 31″ =12diff. ditto ditto		9.814536
Log. 2		0.301030
Nat. num. corres.	1.147741	0.059844
Nat. vers. 22° 48′ 16″ = diff. true alts.	0.078167
Nat. vers. 103° 3′ 23″ = true distance	1.225908

De l’Influence des Agens Physiques sur la Vie. Par W. F. Edwards, D.M., Membre associé de l’Académie royale de Médicine de Paris, Membre de la Société Philomatique, de la Société de Médicine de Dublin, &c. [◊]

THE researches of science among the phenomena of the physical world have long obtained a high degree of estimation and interest in general society; but it is of late years only that their application to living functions has attracted much of the attention of the literary world.

The laws which govern the action of animal organs (the proper department of Physiology) have usually been investigated by the medical profession, to which they especially [p138] refer. Now we find the public take some pains, and with reason, to inform themselves upon subjects connected with physiological knowledge. A well-educated person, disposed to philosophical inquiries, is not merely contented with the consciousness of living, and the common information he derives of its means by experience, but he seeks also to comprehend the relations subsisting between his own organisation and the matters with which he is surrounded, and which at once furnish him with nutrition, life, and support, and assail him with disease and annihilation. His own instincts and observation, joined to the more learned experience of his medical advisers, help him through the precarious stages of life, and these may perhaps be sufficient for all its purposes; and under this impression many will seek to know no more of the secrets of nature.

But we live in an inquiring and scrutinising age, when the demand for scientific principles is very generally urgent. All, therefore, relating to organisation seems of equal interest with that appertaining to what is termed the physical creation or inert matter.

Under this impression we have perused the book before us with great satisfaction, and propose to present our readers with an analysis of the valuable materials which it contains. We have some knowledge of Dr. Edwards, a countryman domiciliated in France, and long resident in Paris. We have confidence in his reports, and highly estimate his philosophical skill, extensive acquirements, and accuracy of observation, ranking him among the first physiologists of the age.

The work, now under consideration, contains an elaborate account of a long series of experiments, instituted for the purpose of ascertaining the influence of the physical agents upon animal life. These agents comprehend the atmospheric air, water, and temperature; the two first constituting the media in which all animals exist, and the last influencing in common the inhabitants of both media. It is true, this is a subject by no means new, for it has engaged the attention of experimenters from the earliest days of science. But Dr. Edwards has diligently and patiently sought to investigate the subject himself, to correct previous errors, and to embody the facts which he has accumulated into a more complete and regular system than heretofore adopted. In this attempt he has been eminently successful, and has effected more perhaps than all who preceded him, availing himself, nevertheless, of the experience of former inquiries.

The extent of his book, and the number of the experiments [p139] are indeed somewhat appalling, but his clear and distinct method of arrangement greatly facilitates the reader’s endeavours to master the extensive subjects of his pages. As a book of reference it should find a place in the library of every scientific society, and no individual devoted to philosophy should omit the possession of it.

The agency of the air around us, water, and heat and cold, have often been the objects of chemical inquiry, from their known great influence upon the animal economy. The changes effected by the phenomena of animal life upon these agents have been accurately examined, and partly reduced to a mathematical precision of calculation.

Spallanzani and others have viewed the subject as it regards physiology, but with such results as left the field open to subsequent investigation. Dr. Edwards seems to have seized upon the deficiencies of his predecessors, and, by going over their ground, and extending his own inquiries, he has arrived at most interesting and important results. These he has divided into four parts, as they relate to the different orders of the animal creation. The first part includes some of the lower animals, particularly tenacious of life, and of cold blood, such as frogs, toads, and salamanders. The second part is devoted to other animals of cold blood, and of the vertebrated order, as fish, and those reptiles which include lizards, snakes, and turtles. The third part refers to warm-blooded animals; and the fourth part of the work is dedicated to the influence of the physical agents upon the human race and vertebrated animals. To these the author has added the discoveries of modern times, relative to electricity on the animal economy, in an Appendix. A collection of tables is appended to the work, exhibiting the principal series of his experiments, as they regard the relative influence of physical agents on the duration of life, and the phenomena resulting from their mutual action.

The great importance of the four grand divisions of the work forbids our hastily reviewing them, and we will endeavour to condense so much of the information they contain as may forward the objects of our analysis. Dr. Edwards thus announces the arrangement of his work:—

“Ces recherches auront donc rapport à l’air dans les conditions de quantité, de mouvement et de repos, de densité et de raréfaction; à l’eau liquide et à la vapeur aqueuse; à la température, dans ses modifications de degré et de durée; à la lumière et à l’électricité. Ces causes agissent à la fois sur l’économie animale, ordinairement d’une manière sourde et imperceptible; et toujours [p140] l’impression qu’on reçoit est le résultat de toutes ces actions combinées.”

“Lors même que, par l’intensité de l’une d’elles, il nous arrive de distinguer la cause qui nous affecte, l’observation de l’effet se borne le plus souvent à la sensation, et les autres changemens qui l’accompagnent nous échappent. On conçoit par la que l’observation la plus attentive des phénomènes tels que la nature nous les présente, ne saurait démêler dans cette combinaison d’actions l’effet propre à chaque cause, ni reconnaître des effets qui ne seraient pas révélés par la sensation.

“Il est une méthode qui règle les conditions extérieures, qui fait varier celle dont on veut apprécier l’action, et qui fait juger, par la correspondance entre ce changement et celui qui survient dans l’économie, du rapport de cause et d’effet: c’est la méthode expérimentale; c’est celle que j’ai suivie. Pour en tirer parti il fallait, d’une part, déterminer l’intensité de la cause, d’autre part celle de l’effet. La physique nous fournit ordinairement les moyens de remplir la première indication.”

In the true spirit of philosophical investigation, Dr. Edwards, in the first place, proceeds to examine the action of physical agents upon the simplest forms, and least elaborately developed organised beings, extending his inquiries upwards, in the scale of the animal world, to man, the most perfect creature, and the ultimate object of all physiological researches.

The peculiarity of constitution belonging to cold-blooded reptiles, among which there is so little mutual dependance of organs, renders these the best tests of the relative and proportionate influence of the different agents, the intense action of which is liable to destroy the more perfect animals; and the great development of the nervous system in the higher orders gives them a wider and more acute range of sensibility. It is difficult, at all times, and often impossible, to insulate corporeal functions among the warm-blooded classes, so as to ascertain the amount and limits of physical agency. The four classes of vertebrated animals, or such as are furnished with true spines, afford ample means of comparative illustrations; and these departments have engaged the author’s attention, in order to display the result of the action of the same agent exercising a uniform influence upon constitutions very differently constructed. The air, for example, exercises its influence uniformly upon he four mentioned classes of vertebratæ, and their different families are similarly exposed to the action of the atmosphere by respiration.

Curious and interesting as is this subject, it is singular [p141] that, while it was among the first to be noticed, it has been the latest in producing satisfactory results. Among the opposing causes of the advancement of knowledge in this department, the ignorance of our ancestors in chemical science seems to be the principal. Without chemical aid it is perfectly useless to attempt the investigation. The composition of the air respired must be well understood; the different gases must be carefully examined, or the physiological inquiry will be darkened and obscured.

Dr. Priestley laid the foundation of our chemical knowledge of gases in their relation to respiration; but some time elapsed before it was understood in what manner the air was connected with animal organisation. Oxygen gas, one of the known constituents of atmospheric air, was Priestley’s discovery, in its effect upon the blood, of converting this fluid from a dark purple to a bright crimson. Lavoisier founded a chemical theory upon this discovery of the agency of air, which was subsequently applied by Goodwin to physiology. The latter author demonstrated, by a series of excellent and correct experiments, that the exclusion of atmospheric air produces death in animals, in consequence of the dark-coloured blood usually circulating in the veins being prevented from becoming crimsoned. The state in which any animal may be thus placed, is known by the term ASPHYXY, and by which is to be understood a deficient or suspended aërification of the blood, from whatever cause it may proceed that the atmospheric air is prevented from access to the blood as it circulates through the lungs.

The great French anatomist, Bichat, pursued this subject still farther, and published a treatise on Asphyxy. He sought, by numerous experiments, to determine the threefold relation of the air to the nervous system, respiration, and the circulation; and he arrived at this great and important conclusion, that the VENOUS OR DARK BLOOD CIRCULATING THROUGH THE BRAIN, CREATES A CESSATION OF THE FUNCTIONS OF THAT ORGAN, AND THAT IN CONSEQUENCE THE HEART LOSES ITS ACTION. This discovery shows us at once the direct cause of asphyxy in all its different degrees, according, in effect, to the vitiated state of the blood from its deficient or suspended aërification.

Le Gallois also investigated the subject of asphyxy; and he found that, when dark blood circulated through the spinal marrow, the motions of the heart ceased; and thus he not only determined the relations of the nervous system to atmospheric air, but also those of the respiration and the circulation, [p142] explaining the action of the air upon animals physiologically.

In this inquiry warm-blooded animals were almost exclusively referred to.

Spallanzani certainly investigated the action of the air on animals of cold blood, but less in relation to the three grand objects of Bichat and Le Gallois; and Spallanzani had the misfortune to live in an age when neither chemistry nor physiology had made such advances as the present age has produced.

Messrs. Humboldt and Provençal have, indeed, supplied much of this deficiency, by their researches into the respiratory functions of fishes. Nevertheless, the ground was still open, and our author has justly appreciated the extent of former inquiries, and observed that the phenomena of cold-blooded animals were too extraordinary to be noticed lightly, and required much more extensive observation than was previously bestowed upon them. With this impression, he proceeded to form an estimate of the comparative influence of the air and water upon the nervous and muscular systems of cold-blooded animals, which the singular modifications of life among reptiles in particular afford ample means of ascertaining.

We know that these animals possess the extraordinary property of existing a considerable time after the removal of the heart, with the free exercise of their senses and of voluntary motion, notwithstanding the suppression of the circulation. Dr. Edwards accordingly selected salamanders for his first investigations, and removed the heart, with the bulb of the aorta. Two of these were exposed to the free action of the air, and the other two were submersed in water previously deprived of air by boiling; a similar temperature being maintained in each medium. In four or five hours, those submersed in the non-arëated water ceased to be active, unless irritated, when they still appeared to retain voluntary power. One died in eight, and the other in nine hours. The salamanders in air lived from twenty to twenty-six hours and upwards. These comparisons were frequently repeated, and upon frogs and toads, with the same results, showing the experiments in air to be far more favourable to their existence than with the animals submersed in the water. Eight hours were about the maximum of the duration of life among the animals submersed in the water, and twenty-nine among those exposed to the air; so that, independently of respiration, the air is thus proved to be the most proper [p143] medium for the action of their nervous and muscular systems, in their insulated state, the respiration and the circulation of the blood being both suspended. As a further corroboration of the superior vivifying property of the air over simple water, when the same animals were plunged into unaërated water during a certain time, as soon as they were, removed into the atmosphere, they instantly revived; and their nervous and muscular systems were acted on according as they were placed in either medium. Dr. Edwards also confirmed the observation of Goodwin relative to the effect produced on the colour of the blood. Properly speaking, the asphyxy comes on the instant the air is excluded, the shades of difference in the colour of the blood being referrible to the air left in the lungs after cessation of respiration.

The next point to determine was the influence of the air upon the same animals exercising the respiratory function, and retaining their circulation, compared with those deprived of these functions.

The difference of time in the two cases developes the influence which the general circulation of the blood, free from aërial contact, exercises upon the nervous system.

To ascertain this point, an equal number of frogs, deprived of the power to exercise their respiratory and circulating functions, together with others left entire, were respectively plunged into disaërated water. At times the difference in favour of the untouched animals was twenty-four hours in favour of the duration of life. Similar trials with toads and salamanders produced the same results. In each case asphyxy came on; but the existence of the animals which lived without the respiration and circulation was much shortened. Thus the relative powers of life between the sole and insulated action of the nervous system, and its action combined with the circulation of dark blood, were estimated. The inference to be deduced, therefore, is, that although disaërated blood furnishes but an ephemeral sort of existence, it nevertheless exercises a comparatively favourable influence upon the nervous and muscular systems, since it tends to the prolongation of the action of these animal functions.

Dr. Edwards next proceeds to investigate the phenomena of asphyxy produced by strangulation, or the mechanical obstruction to the access of air to the lungs, and consequently to the blood. The same animals were employed. When the windpipe was rendered impervious by ligature, the muscles of the animals seemed to be paralysed directly; and although their motions became subsequently revived at times, [p144] they never altogether recovered their perfect freedom. As a comparative illustration, an equal number of frogs were submersed in water, all of which died in about ten or eleven hours, while those which were strangled lived from one to five days. Salamanders continued active longest, and one did not cease to exist till the eleventh day, although during this time he was in a complete state of asphyxy from perfect strangulation.

Dumeril once found that a salamander lived a long time after decapitation, even when the cicatrix of the wound was healed so as to stop all access of air to the lungs.

In comparing the effects of strangulation with those of submersion or drowning, it is to be supposed either that these animals exist a limited period without the necessity of the nervous system being in contact with atmospheric air, or that the air influences their blood through the integuments of the body. Accordingly Dr. Edwards put this to the test by making experiments upon cutaneous respiration.

Spallanzani found that the exposure of cold-blooded animals to the air was attended with exudation of carbon, a phenomenon similar to that of respiration. There appears, however, to be some source of error in these experiments, for Spallanzani removed the lungs, and this operation rendered the animal liable to the absorption of air and loss of blood. Dr. Edwards sought to effect the same purpose by a different and more successful measure. He also confined frogs in vessels of atmospheric air, and fastened bladders round the head and neck, tight enough to stop the entrance of air to the lungs. At the expiration of two hours the air was examined in the bladder, and it was found to contain an excess of carbonic acid. The same result was obtained from salamanders. It appears, therefore, that while air is in contact with the skin, carbon is given out; but whether this be the effect of exhalation merely, or that oxygen is actually absorbed, and carbon transpired, is a question which led to further inquiries. Dr. Edwards, therefore, inclosed cold-blooded animals in solid substances, in order to determine the influence of dark-coloured blood, free of all external agency, in the production of chemical changes, and to observe its sensible effect upon the nervous system.

In the year 1779 three toads were confined in a box hermetically sealed, and so deposited in the Academy of Sciences. Eighteen months after, the box was opened, and one toad was found dead. These animals have been found alive in blocks of coal after an imprisonment of some years, and have [p145] also been sealed up during similar periods without perishing. Possibly some hole or crevice might have admitted a little air. But, in Hevissant’s experiment of 79, care seems to have been taken to obviate this suspicion.

Dr. Edwards, however, determined to put the question to the test. He enclosed ten out of fifteen frogs in thick wooden boxes, and filled the interstices with plaster, covering them over with the same substance, the toads lying each in a central hole or bed. The other five toads were at the same time submersed in water, and at the expiration of eight hours they were found to be dead. In sixteen hours more, one toad was taken from a box and found to be lively, and was reconsigned to its prison. On the sixteenth day the toads in the boxes were discovered alive, and thus the fact was established that these animals can live far longer in a state of asphyxy confined in solid substances, than when submersed in water. This was confirmed by repeated trials on salamanders, frogs, and toads. The frogs perished quickest.

Thus an extraordinary fact is established, as regarding reptiles, since it affords an exception to the general rule that all animals require a CONSTANT supply of fresh air for the maintenance of their existence.

Similar trials were repeated in sand, and with the same results.

Dr. Edwards found that although a certain quantity of air enters the boxes and sand, yet that it is far too little to maintain life. His conclusion, therefore, stands, that animals of the kind employed can live longer in solid substances than in a limited quantity of dry air.

It remains, however, to be considered in what manner these animals have their lives extended beyond those exposed to the action of a body of air. Dr. Edwards supposes the moisture of the sand to be one cause, since in the dry air the animals become desiccated, the cutaneous transpiration being lost in one case, and retained in the other, by the exclusion of air. A rapid and abundant transpiration from the body, united with deficiency of air, seems to be a greater cause of dissolution than confinement in solid substances wherein there is no waste by transpiration.

The author’s inquiries are next directed to the influence of temperature upon animals of cold blood, and two and forty experiments are practised upon this subject, from the month of July to September following, during which period frogs were submersed in aërated water, with a view of settling the duration of life, acted on by varieties of temperature. The [p146] continuance of life, generally, in these experiments, varied from one to two hours and twenty-seven minutes. The mean term of life was one hour and thirty-seven minutes, as averaged in July, and in September one hour and forty-five minutes, the two extremes of the seasons approximating the effects. The duration of the frog’s existence was greatest in the greatest depression of temperature. Thus at ten degrees the duration of life was more than double what occurred at sixteen or seventeen degrees, and at zero it was about triple. As the heat was increased, the duration of life was diminished; at forty-two the frogs died, and in the lowest temperature they lived longest.

It appeared that at zero the frogs did not become stiffened, but retained their motion, and their resistance to the frozen state is the cause of the continuance of their existence at a low temperature. The cause of this resistance is to be found in their peculiarity of constitution. Toads produced similar results.

It may be alleged that frogs naturally live in climates at from forty to forty-two; but, it is to be observed, that they are then placed in a situation of liberty to come to the surface of the water to respire when they please; whereas in these experiments their respiration is limited, from their inability to reach the surface.

Taking a wider range of temperature, Dr. Edwards sought to ascertain the influence of the seasons. In July and September frogs were found to live from one to two hours and twenty-seven minutes in aërated water at fifteen and seventeen degrees. In November they died at the end of more than double this period, under the same temperature, and all other circumstances being similar excepting the season. As the autumn advanced life was prolonged.

To what are we to ascribe the modifications of the seasons? Probably to circumstances appertaining to the intensity of light, to electricity, to temperature, to the pressure of the atmosphere, to dryness and moisture, &c.? Such existing causes naturally suggest themselves. But it appears that little or no account can be rendered as to pressure, since its variations were too trifling during the two seasons. Moisture could not effect an influence, because the experiments were performed in water. The motion of the air was also obviated. Of all the suggested modifications temperature alone acted, and this, as it related to the surrounding air, was rendered ineffectual by artificial temperature. The animals, therefore, could only be affected as to the temperature of the [p147] seasons by that which preceded the experiments. The modifications of the seasons, therefore, appeared to influence the cold-blooded animals used in the experiments in this point of view only. Accordingly we have this remarkable result, that the animals lived twice as long in autumn as in the summer preceding, when plunged in water of equal temperature. The seasons evidently influence their constitutions, so as to extend the duration of life independently of other causes, that is, from summer to autumn. Dr. Edwards endeavoured to ascertain if it proceeds from atmospheric temperature, and he found that frogs lived in aërated water at ten degrees, during November, from five or ten to eleven, and even to forty hours, in some instances, the last term being about double the duration of life in water of the same degree in summer. This proves the remarkable dependence of the frog’s life under water, and the temperature of the month preceding. Two curious facts are thus developed by experiments instituted at different seasons. First, the influence of the temperature of the water in which the animals were placed; and secondly, the influence of the temperature of the air during certain periods preceding the experiments, for in autumn the duration of life was about double that of summer, and in winter he found the term to equal autumn, the temperature of the air being in each comparative experiment artificially raised to the same degree.

It appears from the foregoing experiments that frogs, toads, and salamanders, exist in water according to its lowness of temperature, and that their lives are prolonged by the temperature which precedes the experiment being lowered. It then becomes a question, what are the limits of this influence? This is to be ascertained by observing the greatest duration of life among animals deprived of external air by submersion in water; and noticing at the same time all the favourable circumstances dependent on the concurrent temperature in prolonging life among the cold-blooded animals.

A point relative to the natural history of frogs first presents itself to our notice. Spallanzani is of opinion that frogs do not pass the winter under water, but retire in October from their native rivers into moist sands, in which they make openings to breathe the air through, called by the Italian fishermen il respiro della ranà.

M. Bose, and other French naturalists, found that frogs retire from October to spring into water, but they give us no direct proof that they constantly remain submersed. The presence of the observer may alarm the frogs, and thus prevent [p148] their putting their heads above the water, so that the assertion is but a negative kind of proof that they remain so long under the water without coming up to respire, as some affirm. M. Bose declares he watched frogs approach the surface at regular periods every day during the winter season. Under the most favourable circumstances Dr. Edwards found that frogs could not remain submersed, in winter, more than two days and a half. Frogs are less active during winter than at the other seasons, but they never lose their motion. Were it true, as Spallanzani thinks it is, that they remained so long under water, it is probable that they would become frozen in winter and die. Spallanzani derives his opinion from what occurs with fish, forgetting that frogs are amphibious, and live as well on land as in water; whereas fish are limited to a watery medium, and can, therefore, furnish no example.

Dr. Edwards found that frogs, placed in certain quantities of aërated and non-aërated water of an equal temperature, lived longest in the former; but that the difference was not constant in its results, being often twice as long in one case as in the other, as to the duration of life.

The next inquiry regarded stagnant water renewed at intervals, and in this the duration of life was prolonged beyond the term of the last experiments, and even to eight days. During winter when the temperature was lowest the frogs remained active, though less so than in spring.

The conclusions to be drawn from these experiments are, that frogs pass the winter in an animated state in water, not becoming stiffened as in ice, and that they need not to approach the surface of the water in order to respire, provided the water they inhabit be renewed at intervals; but if the water be not renewed, or if disaërated water be employed, the frogs perish.

Considering that these animals are truly amphibious, these results are very curious; and it is interesting in a physiological point of view, to know that frogs are able to respire the air contained in the dense medium of water for an indefinite period, and just as easily as they breathe the finer medium on land.

Respecting the action of aërated water on the skin, the conclusion drawn seems to be correct, that it must be from cutaneous absorption that the air contained in the water promoted the continuance of life in Dr. Edward’s experiments upon this point, since the animals were in a state of asphyxy regarding respiration by the lungs; and that no [p149] air entered in combination with water was shewn from Dr. Edwards never having seen water in the lungs. Therefore, unless the air acted on the blood through some other organ, the lives of these animals would be definite and shortened, even though the water be renewed from time to time, and their asphyxy would be complete and continued. And since the skin is the only organ in contact with the air, it is fair to conclude that it is the medium of aërial absorption.

When the webs were examined under water, these membranes indicated the action of air upon their blood-vessels, by the bright tint of the blood.

Spallanzani imagined that frogs perish sooner in running than in stagnant water; but Dr. Edwards having secured some of these animals in ten feet of the Seine, whilst others were simultaneously placed in unrenewed stagnant water, he found the latter did not survive many hours, and the former lived a long time.

In order to fix the limits of this kind of existence, frogs were placed in renewed aërated water, and with a temperature never forced beyond ten degrees they were found to live in all seasons of the year; but when the temperature was elevated from twelve to fourteen, they died in a few hours. In running streams they lived longest, and at twelve degrees they were thus more favourably placed than in stagnant water, at a lower temperature even, and taking the precaution to renew the water daily; and at seventeen degrees in running water they died prematurely. Toads exhibited the same comparative results, but they lived the longest.

It appears, therefore, that water contained in vessels is less favourable to the lives of these animals than running streams, although the water and the temperature were identical. Probably the great advantage of running water is its constant and unceasing renewal. The separate and comparative influence of air, water, and temperature, being thus investigated, the combined action of the three physical agents was next inquired into, and it is demonstrated that frogs submersed in water are influenced by three circumstances,—1. the presence of air in water; 2. the quantity of its renewal; 3. the temperature of the medium. If the manners of frogs be closely examined, they appear to live in water under very considerable influence from the atmosphere.

From circumstances developed in the foregoing experiments, cutaneous respiration seems to be pretty evidently indicated. A chapter is, therefore, devoted to this subject, one that is not well known, although pulmonary respiration is [p150] generally understood. In frogs, the function of pulmonary respiration is united with that of deglutition, and the air enters only by the nostrils, the mouth being closed during respiration. While the mouth remains open, the action of deglutition is stopped, and, therefore, the animal does not then breathe. Dr. Edwards availed himself of this circumstance by gagging the mouth so as to keep it open, and thus prevent the air from entering the lungs. The frogs were sufficiently exposed to moisture and renewal of air to their bodies: the results were, that, at twenty-four degrees, five frogs so placed died next day, and one lived a week.

Dr. Edwards immersed some frogs in wet sand, and adopted an improved method of excluding air from the lungs, and some of them lived twenty days. Hence it evidently appears that air influences the skin materially, and counterbalances the asphyxious state induced by obstructing the air’s passage to the lungs. By adopting other methods, the existence of frogs was prolonged to thirty or forty days. It is, therefore, sufficiently proved that the blood undergoes its necessary changes from atmospheric influence through the medium of the skin, although in a minor degree compared with those which it passes through from pulmonary respiration. Frogs are thus shewn to possess a double source of respiration.

By substituting oil for water, frogs immersed in this fluid died in a few hours, being at liberty to breath the air on its surface. And, when plunged into oil, with the means of breathing by the lungs arrested, they lived an equal time with frogs simultaneously placed in water without power to respire. A comparison was instituted with frogs in oil and in water, being allowed to breathe air, when the difference was found to be very considerable in favour of the aquatic bath. These circumstances shew, that, even with the feeble succour of the air through the skin, absorbed from the water, the respiratory function was far more prolonged, than in the case of the obstruction afforded by the oil. Thus we have abundant evidence of the double function by which frogs are maintained, from the action of the air on the skin and the lungs; and this appears to be the means of existence among amphibious animals generally.

It may be asked why these animals die in deep water when prevented from approaching the surface? It appears that, having expelled the respired air from their lungs, which is imperfectly renewed from the water, they become specifically heavier than the water, and unable to rise from the bottom; and thus placed, the duration of their lives depends upon [p151] the resistance offered by their constitutions to the depressing effects of a state of asphyxy while remaining submersed.

Dr. Edwards next proceeds to inquire into the effects of TRANSPIRATION. A liquid transfusion from the skin of animals is constantly going on, either in the form of vapour or of fluid in a denser state.

The latter constitutes sweat. This phenomenon exhibits great variations, and it is important to know what diminution of weight the body suffers in different circumstances. In the course of an hour remarkable fluctuations occur.

Dr. Edwards suspended frogs, toads, and salamanders, in a calm air, weighed them, and noted the results, which, though very changeable in an hour, were generally uniform in three, and in nine hours they averaged an equal result. The successive diminution in the mass of fluids was evident.

The results were modified by the alternate position of the animals in a body of air in repose, or agitated by a draft. And these results do not appear to depend upon any principle of vitality, for they take place equally in death and in life, and indeed among unorganized bodies, as, for example, lumps of charcoal soaked in water. Therefore the cause of the phenomenon of transpiration seems to be referrible entirely to physical agents. The motion of the air seems to be its exciting cause; for even when, to all appearance, it is calm, it is in reality agitated more or less, and produces a sensible evaporation from the skin. But the difference between the effect of calm and agitated air is remarkable; for in a draft, the animals exposed to it sweated away double the quantity of liquid compared with those confined in a room shut up. The amount lost was proportioned to the intensity of the wind, and reached a triple amount over those animals in stagnant air; and this fact explains the variations noticed from hour to hour among animals exposed to currents of air.

The transpiration which occurs in very moist air, always amounts to a diminution of weight; but in dry air it is five or ten times greater; and when the influence of a moist state of the atmosphere is compared with that of a dry state, the amount of evaporation is equal to that of a dry and calm air.

Transpiration may, therefore, be referred to the agitation of the atmosphere for its exciting cause, beyond any modifications of its density. And, although an elevated temperature be favourable to transpiration, its modifying influence is less than that of other causes.

In comparing the effects of absorption and transpiration, [p152] in water and in air, frogs were found to gain an addition to their weight according to the term of their continuance in the former medium. An absorption of water was rendered evident by the loss of bulk it had sustained, when measured after the experiment.

Thus, when the comparative influence of water and air is estimated, the former appears to be absorbed, and adds to the weight of the body; and the latter tends to diminish the weight, by different and fluctuating degrees of evaporation taking place, and dependent much more on the degree of motion in the air, than on its dryness or humidity: these last conditions modify evaporation in a minor degree, when compared with the influence of a current of air.

The celerity of absorption exceeds that of transpiration six times, in the most rapid cases. It therefore results, that the losses by transpiration in air should be repaid by absorption of water in a much less time than the expenditure occurs. But the decrease of weight is not prolonged; it is sudden, and not continuous, alternating with augmentation of weight, by absorption of liquid going on in a ratio superior to the loss; and thus nature’s provision is manifested for the nutriment of the body.

With this last inquiry Dr. Edwards concludes the first part of his work; and it is observed, that, with regard to transpiration, the losses of weight have been considered without reference to the existence of any other influence than water. The losses by transpiration have been examined generally without regard to the matters lost. What relates to water differs essentially in one respect from that which regards the air. The losses sustained by the body ought to be more particularly examined. Temperature and loss of time require estimation. An excretion of solid matter evidently takes place; for the water, in which animals are submersed, becomes turbid, especially in hot weather, and it sensibly contains animal matters, affecting the weight of the body in water.

When animals are submersed in water, their skins exercise two functions, acting inversely in determining their weight. And it results, from comparative experiments, that the absorption at zero exceeds the loss in water; while at thirty degrees the loss exceeds the increase by weight from absorption; and the higher the temperature, the greater is the excess in the discharge of animal matters. We may therefore presume, that the agency of temperature produces analogous effects, upon aërial transpiration, to those before observed [p153] in other inquiries; and the effects of dryness and moisture in the air produce a minor degree of influence also, when compared with temperature, on the losses of animal substances.

We have been thus minute in our analysis, because the subject of it is new to science in its present shape, and of a high degree of interest. Dr. Edwards’s researches among the different classes of animals have tended more to the illustration of the influence of physical agents upon life than any previous authorities; and the persevering industry, accuracy of observation, and patient inquiry which he has evinced in his investigations among cold-blooded animals, have placed this department of the creation in a point of view at once curious, interesting, and valuable to science. We attach the greater importance to this part of the author’s work, as it is a ground on which he may be consulted, and quoted as indisputable authority, until equal inquiries have shewn him to be fallacious.

Our limits will not at present permit us to proceed farther in our analysis, and we must refer the remainder of the book to a future opportunity. The subjects of the three other parts, though greatly extended, will not probably require such minute analysis as those novel experiments which form the subject of the first part; but we imagine that the application of the principles laid down, in the previous inquiries, to human physiology, will be found not less interesting than those which relate to the natural history of the lower orders of the animal creation.

An Account of Professor Carlini’s Pendulum Experiments on Mont Cenis. [◊]

WE believe that no account of Professor Carlini’s pendulum experiments on Mont Cenis has hitherto appeared in the periodical scientific publications of this country: the experiments are, however, well deserving of such notice, having been conducted with great care, and having had a specific object in view, which object seems to have been satisfactorily accomplished. The following brief account of them, taken from the original memoir published in the Appendix to the “Ephéméride di Milano” for 1824, may not be unacceptable to those of our readers who interest themselves in subjects of this class.

The length of the simple pendulum vibrating seconds is a [p154] measure of the intensity of gravitation; i. e. of the excess of the force of gravity over the centrifugal force. In consequence of the ellipticity of the earth, and of the difference in the direction of the two forces, the intensity of gravitation varies according to the different latitudes. It also varies, in the same latitude, according to the greater or less elevation of the pendulum above the level of the sea; i. e. according to its greater or less distance from the centre of the attracting force.

Had the earth a perfectly level surface, such, for instance, as it would have if it were everywhere covered by a fluid, the force of gravity, in receding from the surface, would diminish in the duplicate proportion of the distance from the earth’s centre. In the actual state of the globe, however, its continents and its islands are raised above the general level of the sea by which it is only partially covered; and if a pendulum be raised, on the surface of the land, to a known elevation above the sea, the diminution of gravity will not be, as in the more simple case, proportioned to the squares of the respective distances from the earth’s centre, but that proportion will require to be modified, by taking into account the attraction of the elevated materials, interposed between the general surface and the place of observation.

When pendulums are employed in different latitudes, to obtain the ratio of gravitation between the equator and the pole, for the purpose of deducing the ellipticity of the earth, all the places of observation, being on land, are more or less elevated above the sea; inland stations, in particular, are sometimes at considerable elevations: to render these results comparable one with another, it is necessary to reduce each result to what it would have been, had it been made at some level common to all the experiments; and the surface of the sea has hitherto been taken as that common level. Previous to the publication of a paper of Dr. Young’s in the Philosophical Transactions for 1819, the consideration which we have mentioned, that of the attraction of the matter interposed between the place of observation and the level of the sea, was generally unheeded in estimating the allowance to be made for the reduction of different heights to the common level: in that paper, however, Dr. Young took occasion to point out the probable effect of [p155] the interposed matter in modifying considerably the usual allowance; that, supposing its density to be about half the mean density of the earth, the effect of an hemispherical hill of such matter, on the summit of which the pendulum should be placed, would be to diminish the correction, deduced from the duplicate proportion from the earth’s centre, about 15; that, in like manner, a tract of table-land, considered as an extensive flat surface, of the same relative density, would diminish the correction about 38; and that, accordingly, in almost any country that could be chosen for the experiment, the proper correction for the height would vary, according to the form and density of the interposed materials, from rather more than a half to rather less than three-quarters of the usual allowance. This view has been subsequently acted upon by the English pendulum experimentors, in reducing their observations; but it has not been yet adopted by the French. The experiments of Professor Carlini were calculated to afford a practical illustration of the correctness of Dr. Young’s reasoning.

Professor Carlini was engaged, in the summer of 1821, in concert with Professor Plana, in determining the amplitude of the celestial arc between the Hospice on Mont Cenis and the Observatory at Milan, by means of fire-signals made on the Roche Melon, and observed simultaneously at Milan and at a temporary observatory established at the Hospice. Whilst thus engaged, Professor Carlini, being stationary for several days on Mont Cenis, and obliged to have time very accurately determined, for the purpose of comparing with the observatory at Milan, availed himself of the opportunity to employ a pendulum apparatus of the same general nature as that used by M. Biot at Paris, which had been prepared at Milan some years before, under the direction of a commission of weights and measures, with the view of determining the value of the divisions of the national linear scale. As this apparatus differed in some few particulars from the original employed in France, we shall briefly notice the differences, presuming our readers to be acquainted with the apparatus of MM. Borda and Biot.

1. In the Milan apparatus, by means of two microscopes furnished with wire micrometers, the length of the pendulum [p156] may be measured without touching it; without approaching it; without even opening the case which contains it. The measure is obtained by bringing the wires in contact with the images of the knife-edge suspension, and of the upper and lower borders alternately of the platinum disk suspended to the thread: thus preventing the risk of deranging the equilibrium, and avoiding the effect which the heat of the body might have on the dilatable metallic thread.

2. The half sum of the distances taken between the suspension, and the upper and lower edges of the disk, gives the distance of the centre of the disk itself; without measuring its diameter with a compass, an operation exceedingly difficult to execute with the necessary precision. By this apparatus of microscopes the length may be measured at pleasure, even during the time of oscillation; and being attached to the wall, instead of supported by the floor, the risk of derangement by the tread of the observer is avoided.

3. The pendulum, and the clock by which its oscillations are measured, were not, as usually, near together and resting on the same base, but were perfectly separated. The coincidences of the oscillations were observed, by bringing the image of the pendulum of the clock, reflected by means of an oblique mirror, in contact with the image of the simple pendulum seen direct through a telescope. By this modification the risk of the mutual influence of the pendulum and the clock is avoided.

4. The disk was attached to the thread by means of knots in the thread itself; avoiding the correction for the small cup usually employed for that purpose.

5. An alteration was made in the weight and shape of the knife-edge suspension; reducing its weight to about 10 grains, and giving it the shape of a rotella, instead of that of a triangular prism.

The simple pendulum and microscopes were attached to a strong wall, in a room on the ground floor, contiguous to the temporary observatory, and well sheltered from the sun and weather. The clock with which the pendulum was compared, was supported by a pyramid of masonry resting on the ground, and occupying the middle of the room. The experimental length between the microscopes was referred to three standard metres, [p157] in perfect agreement with each other: one received from Paris by the Commission of Weights and Measures at Milan; a second brought more recently from Paris by Conte Moscati; and a third in the possession of the Royal Academy of Turin.

The experiments were commenced on the 3rd of September, and terminated on the 27th, being interrupted by M. Carlini’s absence at Chambery from the 7th to the 12th. The distance between the microscopes, and the oscillations and length of the pendulum, were measured alternately. Thirteen independent results were thus obtained, of which the greatest discordance from the mean was not more than 1310000ths of a British inch. The mean result was 39.0992 British inches, the length of the pendulum vibrating seconds in a vacuum, at the place of observation on Mont Cenis, 1943 metres, or 6374 feet above the sea, in the latitude of 45° 14′ 10″. To compare with this determination, we may obtain a tolerably fair approximation to the pendulum at the level of the sea in the latitude of 45° 14′ 10″, such as its length might have been found, if the mountain could have been removed and the pendulum placed on its site, by deduction from the lengths actually measured with a similar apparatus, on the arc between Formentera and Dunkirk, at stations not far removed from the level of the sea, in the adjacent parallels to Mont Cenis, and in the countries adjoining. Of these there are five, not including the station at Clermont, in consequence of its great elevation: they are as follows:—

Dunkirk	51° 02′ 10″;	its pendulum at the level of the sea =	39.13771
Paris	48  50  14 ;	ditto	39.12894
Bordeau	44  50  26 ;	ditto	39.11295
Figeac	44  36  45 ;	ditto	39.11212
Formentera	38  39  56 ;	ditto	39.09176

The mean length of the seconds pendulum at the level of the sea, in the latitude of 45° 14′ 10″, deduced from these determinations, is 39.1154; and it is so equally, whether an ellipticity of 1288th, or of 1304th, or any intermediate ellipticity, be assumed in the reduction.

We have, then, 39.1154−39.0992 = ·0162 inch., as the [p158] measure of the difference in the intensity of gravitation at the place of observation elevated 1943 metres; and at the level of the sea. The radius of the earth, being 6,376,478 metres, this measure, according to the duplicate proportion of the distances from the earth’s centre, should be ·0238 inch. The attraction of the mountain is, then, equal to ·0238−·0162 = ·0076 inch. Whence it appears that, in this particular instance, the correction for the elevation is reduced, by the attraction of the interposed matter, 68100ths, or to about 710ths of the amount immediately deducible from the squares of the distances.

It is obvious that, if we possessed a correct knowledge of the density and arrangement of the materials of which Mont Cenis is composed, so as to enable a computation of the sum of all the attractions which they exercise on the place of observation, this result might furnish, as well as Dr. Maskelyne’s experiments on the deviation of the plumb-line produced by the attraction of Mount Schehallien, a certain determination of the mean density of the earth. Professor Carlini considers that the form of the eminence may be sufficiently represented by a segment of a sphere, a geographical mile in height, having as its base a circle of 11 miles diameter, the distance from Susa to Lansleburgo; the attractive force, on a point placed on the summit, would, in such case, be equal to 2 π δ (1−23 √111) or in numbers to 5·020 δ, δ being the density of the mountain, and 2 π the ratio of the circumference to radius. The attractive force of the earth, on a point at its surface, is 43 π r Δ, = 14394 Δ, r being the radius of the earth = 3437 geographical miles, and Δ its mean density. Now these two quantities, 14394 Δ and 5·020 δ, should be, to each other, in the proportion of 39.1154,—the pendulum at the level of the sea, representing gravitation at the surface of the earth,—to ·0076, the portion of gravitation at the summit of the mountain due to the attraction of the mountain. By the observations of M. de Saussure and other geologists, Mont Cenis is chiefly composed of schistus, marble, and gypsum; the specific gravities of which substances were ascertained, from numerous specimens in the possession of M. Carlini, to be respectively as follows:— [p159]

The schistous	2·81.
The marble	2·86.
The gypsum	2.32.

In the absence of a precise knowledge of the quantity and position or each of these three component parts, we may take the mean, 2.66, of their several densities as approximatively the density of the mountain, = δ. We have then

Δ = 5.02 δ × 39.115414394 × ·0076 = 4.77,

a result differing little from that of Cavendish as recently corrected by Dr. Hutton, and still less from that of the Schehallien experiments.

The most hypothetical element of this calculation is the width assigned to the base of the mountain; but by the very nature of the question, it has but little influence on the final result; since, by even doubling the assigned diameter, the total attraction would not be altered a twentieth. In regard to the mean density of the mountain, if it were taken at 2.75, instead of 2.66, that of the earth would result 4.94, instead of 4.77, as given above.

E. S.

Transactions of the Horticultural Society. Vol. vii. Part 1. 4to. London, 1827. pp. 208. [◊]

---

I. Observations upon the Growth of Early and Late Grapes under Glass. By Mr. James Acon. [◊]

FEW gardens are to be found in which bunches of fresh ripe grapes can be gathered every day in the year: notwithstanding the importance of the fruit to the luxurious, and the facility with which the vine submits to the artificial climate of the forcing-house. Nothing is easier than to secure crops of grapes in a vinery during the spring and summer months; but it is far more difficult to obtain them in the last and earliest seasons of the year, when the plants would [p160] naturally be in state of torpidity. It is well known that this desirable purpose is attained in great perfection in the garden of the Earl of Surrey, at Worksop Manor; and the management there practised is the subject of this paper.

The common methods of forcing early grapes are to train the vines under the roof near the glass, or on small frames against flued walls; but to both these practices Mr. Acon finds great objections: to the former because it renders the house too dark, and exposes the young and tender branches to the pernicious effect of blasts of cold air rushing through the interstices of the panes; and to the latter, because the heat of the flues is apt to scorch the branches, and in consequence to destroy the crop,—excessive heat in the one case producing the same injurious effects as excessive cold in the other. The following are the two modes by which Mr. Acon obtains his very early and his very late grapes. For the early crops a house is used, of which the back wall is 9.6 feet in height, and the front wall 3 feet, the roof forming an angle of about 30 degrees. It is heated, from the absolute necessity of employing an atmosphere of unusually high temperature, with two flues that pass along the middle of the house, and return in the back wall; a fire-place being built at each end of the house. Forcing begins on the first of September, and the fruit begins to ripen the first week in March. The vines are trained upon a trellis, fixed over the flues, in the centre of the house, and also upon the back wall; but none are allowed to obstruct the light by occupying the roof, until about six weeks after the forcing has commenced, when some new shoots are introduced and trained to the rafters. The form of this house gives it a peculiar advantage, in presenting a greater surface for the growth of vines than can be derived from any other plan; the trellis which is placed over the flues is nearly equal to the whole roof, without being in any degree injurious to the plants trained upon the back wall. The vines are planted in the inside of the house, but in such a manner that the mould in which they grow is not heated by the fire-places of either flue. The usual mode of exposing the main stem of a forced vine to an extremely low temperature in the external air, while the branches are stimulated by a very high temperature in an entirely different atmosphere, is very properly objected to. Nothing, in fact, can be more injudicious than such a practice, in cases where very early forcing is required; for it should be borne in mind, that although the absorption of the elements by which the proper juices of a [p161] plant are elaborated, and brought into the state under which they appear in the fruit, and in the secretions of the plant, is carried on by the leaves alone, yet that all these juices have, in the first instance, to pass along the vessels of the stem before they reach the leaves; and that the whole of the bark of a tree is, rightly considered, a leaf of a particular description, formed of the same kind of tissue, and exercising the same functions, and undoubtedly producing a powerful effect upon the motion of the fluids of the branches, with the vessels of which it is elaborately and intimately entangled, from the core to the circumference. No argument can be necessary to show that an equal action of the vessels of a plant is indispensable to the due maintenance of the vegetable functions in a healthy state, and that this is not to be maintained by exposing the main stem and the extremities to an atmosphere and temperature entirely different. Such irregularities do not exist in free Nature, and she will not submit to them when in fetters.

In pruning vines for early forcing, as little wood should be employed as possible. Mr. Acon stops the shoots one joint above each cluster, and has no joint without a bunch. When the crop is over, and the wood perfectly matured, the branches should be laid near the ground, and shaded till the recommencement of forcing. In short, they should be placed in a condition as nearly as possible resembling the gloom and cold of winter. If this process be well managed, the vines will alter their natural habits, and instead of budding with the spring, their vegetation will naturally commence at the period at which they have been accustomed to be stimulated.

For late grapes, a house of a different construction is employed. The back wall is 12 feet high, the front wall 112 foot, and the roof lies at an angle of 45 degrees. The heat is supplied by a single flue passing along the middle of the house. The sorts best adapted for late forcing are the Muscat of Alexandria, the St. Peter’s, and the Black Damascus; all other kinds wither prematurely. This house is generally shut about the middle or end of May, as soon as the bunches become visible. The vines are trained on a trellis near the glass. Till they are out of blossom the air is kept very warm, a point to which much importance attaches, because it is during this period that all the branches that are to bear fruit in the succeeding season are produced. In a high temperature, the branches will grow more compactly, and [p162] will be more regularly matured than in a low temperature, in which the wood is apt to become excessively luxuriant, and not to ripen well. Great attention must be paid to this point. As much air as possible is introduced into the vinery during the summer; but as the autumn advances, more caution in this respect is observed. The fruit should be perfectly coloured at the approach of the dark season; for if the colouring be deferred too long, the berries will never acquire their proper flavour. Great care must be observed to remove daily such berries as are inclining to damp, or the whole crop will soon be spoiled. This should be particularly attended to; for the contagion of what gardeners call damp, arises from the growth of minute fungi which vegetate upon the epidermis, and spread during the autumn with alarming rapidity from bunch to bunch.

The pruning of vines for late forcing is the same as has been already explained. When the crop is gathered, the house is unroofed for a short time, in order to expose the branches to a low temperature, and to the degree of humidity necessary to replenish their vessels, which have been drained by the dryness of the climate in which, when forced, they were necessarily kept.

By the means above described, a regular supply of grapes is secured through the year. The late-house crop lasts from the middle of January to the end of March; it is succeeded by the first crop in the early-house, which carries on the supply into May, and it is continued by the grapes on the rafters in the same house until the vines in the pine stoves, which are forced early in January and February, produce their crops. These continue bearing through the summer, when a vinery, of which the forcing commences about the end of March, furnishes the supply till the late-house fruit is ready in January.

Upon the whole this may be considered a most instructive and valuable communication.

II. On the Varieties of Cardoon, and the Methods of cultivating them. By Mr. A. Mathews. [◊]

Who does not wish to read of the cardoon; of that prince of vegetables, whose praises have been sung or said by all cooks and gourmands, from the fastidious Périgords and Cardellis of the French cuisine, down to the more homely Rundells and Glasses of our English kitchens; whose virtues are so marvellous as to be credible upon no less authority [p163] than that of the sage gastrophilists aforesaid. To restore unwonted vigour to old age, and new elasticity to youth, are the most modest of its attributes; the magical broth with which the veins of Æson were replenished by the cunning Medea, was doubtless prepared from the cardoon; and the story itself is probably a sort of figurative record of the skill of the fair enchantress in cooking this delicious vegetable, which was well known to the Grecian gastronomes under the name of κακτος; but this we throw out merely as a suggestion. Upon preparing herbs thus potent for the table, cookery has exhausted all its skill; to dress a cardoon is declared, by the highest authority in the art, to be the surest test of a skilful cook; and one of those invaluable acquirements which, to borrow the words of a writer not less celebrated for his powers of composition than of cooking, “raises cookery to the rank of the sciences, and its professors to the title of artists.” Our good forefathers, indeed, “could not find the true manner of dressing cardoons,” and were content to eat them raw “with vinegar and oyl, pepper and salt, all of them, or some, as every one liketh for their delight;” which, considering that this vegetable is both bitter and astringent in a high degree, does not argue much for the delicacy of palate of our ancestors; little did they dream of the savoury preparations that modern art has devised by the aid of Espagnole, consommé, blancs, tammies, marking, masking, and all the mysteries of the stew-pan.

Four varieties are here described, of which the Spanish cardoon is the most common, and the cardon de Tours the best.

They are cultivated, like celery, in deep broad trenches, well manured and watered. When the plants are nearly full-grown, which will be about the end of October, a dry day is to be chosen for performing the operation of blanching them, which is thus effected:—

“The leaves of each plant are carefully and lightly tied together with strong matting, keeping the whole upright, and the ribs of the leaves together. The plant is then bound closely round with twisted haybands, about an inch and a half in diameter, beginning at the root, and continuing to about two-thirds of its height. If the plants are intended for winter store, they must be earthed up like celery; but if to be consumed before the frosts set in, the operation of earthing up may be omitted.” [p164]

III. Accounts and Descriptions of the several Plants belonging to the genus Hoya, which are cultivated in the garden of the Horticultural Society at Chiswick. By Mr. James Traill. [◊]

The beauty of one species of Hoya, viz., H. carnosa, has long caused it to be a favourite with collectors. The object of the writer of this paper is to call attention to such others as are known to exist in gardens, or as are preserved in the records of the botanist.

The following species form the subject of the paper, viz.:

• 1 Hoya carnosa, R. Brown.
• 2 Hoya crassifolia, Haworth.
• 3 Hoya pallida, Lindley.
• 4 Hoya Pottsii, (Tab. I.)
• 5 Hoya trinervis.

These five are all the species at present cultivated in gardens; others are known to exist in the warmer regions of Asia, where they should be assiduously sought for by travellers, as they are not only very ornamental, but easily to be transported to Europe.

From such materials as he has been able to procure, the writer enumerates the following as completing the genus Hoya, as far as at present ascertained:

• 6 Hoya chinensis.
• 7 Hoya viridiflora, R. Brown.
• 8 Hoya lanceolata, D. Don.
• 9 Hoya linearis, D. Don.
• 10 Hoya australis, R. Brown, MSS.
• 11 Hoya nicobarica, R. Brown, MSS.
• 12 Hoya augustifolia.

The paper concludes with a detailed explanation of the best manner of cultivating Hoyas.

IV. On acclimatizing Plants at Biel, in East Lothian. By Mr. John Street, gardener to the Honourable Mrs. Hamilton Nesbitt. [◊]

Perhaps there is no point whatever, connected with Horticulture, of greater interest than that which forms the subject of this paper; it is the distant goal towards which we all are striving, but of which, alas! we have not as yet even caught a glimpse. The gardener is in possession of the powers by which he can bend the seasons to his will; he can dispel the frozen gloom of winter with the rich warm glow of the vintage; at his call the flowers of spring and summer start up beneath his feet, and his hothouses are filled with the luscious fruits of the torrid zone. All this he knows how to effect with an artificial climate; but he has no influence over the natural climate of his country, nor can he impart to the vegetation of warmer latitudes the least additional power of resisting cold, for which they have not been prepared by nature. Acclimatizing is still a secret to be discovered. To [p165] this day not a single instance can be adduced of any exotic plant whatever possessing greater powers of withstanding cold, than it had when first introduced. It has been hoped that if the seeds of given plant could be procured, for many generations, in a climate severer than its own, the offspring so obtained would gradually accommodate themselves to their new country; but no such result has followed from the experiments that have been tried. Let us take a few familiar examples:—the common nasturtium, (Tropælum majus,) a native of Peru, is said to have been introduced about the year 1686. At the time at which we are writing, it must have descended through about 140 generations; and yet it has not become in the smallest degree capable of resisting cold. Of the mignonette (Reseda odorata), the date of introduction is not well ascertained; it has probably been a favourite border annual for sixty or seventy years, and yet it has in no degree shaken off its annual character, which is unnatural to it, and resumed the suffrutescent habit which it possesses in its own milder climate. The potato, too, which has for two centuries and a half been increased in every conceivable manner, by seeds as well as by offsets, bears cold in no degree more readily than it did in the sixteenth century. Nor does it appear to us probable, that acclimatizing, if practicable, is to be brought about by sowing seeds in northern latitudes through successive generations. We do not believe that plants will bear their seeds at all in a temperature much lower than that in which they have been located by the hand of Nature. The heat of a northern summer sufficiently approximates to that of the tropics, to be considered, with reference to vegetation, as the same, and it is during that season that the seeds of all plants are ripened; the conditions, therefore, under which the seeds of Tropæolum, for example, are produced in England, do not materially differ from those under which the same seeds are produced in Peru; if the season proves unpropitious in any considerable degree, they are not produced at all. How then can it be expected that seeds ripened under similar circumstances, but in different latitudes, should give birth to a progeny differing in any remarkable particular from their parents? In fact, in power of resisting cold, they do not differ at all. If such a capability were to obtained, it would be by inducing plants to ripen their seeds in winter.

But if it is certain that nothing is to be gained in acclimatizing, by raising plants from seed through successive generations, [p166] it is no less true that many trees, which have been supposed to be incapable of surviving a northern winter, are now ascertained to be perfectly hardy, and that the power of enduring cold may be increased in others, by a judicious management of soil and situation.

The phenomenon of vegetable life being destroyed by cold, probably arises from the vessels, through which the circulation and secretion of the fluids of plants take place, being ruptured by the expansion, from cold, of the fluid they contain. In proportion, therefore, to the tenuity of the vessels, and the abundance of their fluid, will be the danger to which they are exposed from frost; and to the strength of the vessels, and the paucity of their fluid, the power of resisting cold. Thus vigorous shoots of the oak, walnut, and many other trees, which are formed with rapidity, imperfectly matured, and highly charged with fluid, are extremely impatient of cold, and are even destroyed by a few degrees of frost; while the twigs and branches of the same trees, which are formed slowly, fully matured, and incompletely filled with fluid, bear unharmed the utmost rigour of our winters. In acclimatizing, therefore, this law should be carefully remembered, and the situations in which tender plants are stationed, should be those in which their growth is restrained, and an excessive absorption of fluid prevented.

This appears to have been the true secret of the success that has attended the attempts at acclimatizing, which form the subject of Mr. Street’s communication. By planting in situations well drained from superfluous moisture, under circumstances where rapid growth was rendered impracticable, and, as we understand, in a garden admirably adapted to the object, from its position, he has succeeded in naturalizing, in latitude 56° N., plants which have not yet been known to endure the winters even of the parallel of London.

V. Upon the Culture of Celery. By Thomas Andrew Knight, Esq., F.R.S., President. [◊]

“That which can be very easily done, without the exertion of much skill or ingenuity, is,” Mr. Knight observes, “very rarely found to be well done, the excitement to excellence being in such cases necessarily very feeble.” This remark is in the present case applied to the cultivation of celery, which, being a native of the sides of wet ditches, might naturally be expected to demand an abundant supply of water when cultivated. Accordingly, Mr. Knight found that by keeping the ground, in which celery was planted, [p167] constantly wet, it grew by the middle of September to the height of five feet, and its quality was in proportion to its size. Mr. Knight also recommends planting at greater distances than is usually the case, and covering the beds, into which the young seedlings are first removed, with half-rotten dung, overspread to the depth of about two inches with mould; under which circumstances, whenever the plants are removed, the dung will adhere tenaciously to their roots, and it will not be necessary to deprive the plants of any part of their leaves.

VI. Report upon the New or Rare Plants which flowered in the Garden of the Horticultural Society at Chiswick, between March, 1825, and March, 1826. Part 1. Tender Plants. By John Lindley, Esq. [◊]

The subject of this paper consisting of botanical details which do not bear curtailing, we shall only extract the names of the new species described in it, as a guide to our botanical readers. In the whole, thirty-three species are noticed; of which the following are published for the first time:—

• 2 Passiflora obscura.
• 7 Solanum dealbatum.
• 10 Tabernæmontana gratissima.
• 13 Tephrosia? Chinensis.
• 15 Hellenia abnormis.
• 16 Gesneria Douglassii.
• 21 Gynandropsis pulchella.
• 23 Rodriguezia planifolia.
• 26 Brassavola nodosa.
• 33 Phycella corusca.

VII. Account of a Protecting Frame for Fruit-Trees on Walls. By Mr. John Dick. [◊]

In order to protect the fruit upon walls from the ravages of bees, wasps, flies, and other winged enemies, a frame is contrived fitting close to the face of the wall, and having a moveable sliding canvass front, which can be readily removed when the fruit is to be gathered, and replaced again afterwards. A plan of the frame accompanies the paper. From what we have seen of this contrivance, we know that it is well adapted to its purpose, and that no garden in which fine fruit is required, should be without one or more of such frames. For the mode of making them, we must refer to the paper itself.

VIII. On the Esculent Egg-Plants. By Mr. Andrew Mathews. [◊]

In this country, the egg-plant, brinjal, or aubergine, is chiefly cultivated as a curiosity; but in warmer climates, where its growth is attended with less trouble, it is a favourite article of the kitchen-garden. In the form of fritters, or farces, or in soups, it is frequently brought to table in all the southern parts of Europe; and forms a pleasant [p168] variety of esculent. This paper describes the only two kinds that are worth cultivation in England.

IX. Notices of Communications to the Horticultural Society, between January 1, 1824, and January 1, 1825. Extracted from the Minute Books and Papers of the Society. [◊]

A novel kind of pine pit is described, which is said to answer every purpose that can be desired. It is heated by flues passing through a chamber, formed by beams extending from the back to the front wall, and so becoming a sort of floor, upon which is first placed a layer of turf; and then the tan in which the pine-plants are plunged. The warmer air is conveyed into the upper part of the pit by means of small apertures contrived in the walls, at four inches and a half apart, both in the back and front of the pit, and also through iron pipes resting on the beams and passing through the tan. The ventilation is effected by air-holes in the front wall, and sliding shutters in the back walls. An explanatory figure accompanies the statement.

The famous rhubarb, which has of late acquired so much celebrity under the name of Buck’s rhubarb, is mentioned as excellent when forced. It is not generally known, that this sort is the genuine Rheum undulatum of botanists uncontaminated by mixture with the common garden kinds. The plant generally called Rheum undulatum, is a half-bred, possessing none of the good qualities of the native species.

George Tollet, Esq., of Betley Hall, in Staffordshire, recommends the preservation of apples for winter store, packed in banks or hods of earth like potatoes. The method is said to be effectual and economical.

Thomas Bond, Esq., of East Looe, in Cornwall, describes his mode of cultivating strawberries. He does not adopt the common practice of cutting off the runners, but they are confined to the bed by being turned back among the plants from which they spring. In the autumn, the beds are covered to the depth of two inches with fresh earth, through which the strawberry plants shoot in the spring with great vigour.

A kind of wicker basket is described, which is cheap and well adapted for screening half hardy plants during the winter. It is fixed in the earth by means of the points of the ribs of the wicker work, which are allowed to project a few inches for the purpose.

It is stated by John Wedgewood, Esq., that good celery may be readily obtained by transplanting seedling plants that have remained in the seed bed, till they had acquired a [p169] considerable size. They grow more vigorously than the younger plants that are transplanted in the usual way.

William Cotton, Esq., of Wellwood-house, describes the good effects of painting an old garden wall with seal oil and anticorrosion paint. The wall in question was covered with trees, which were every year attacked by blight. Since the operation the trees have borne good fruit, made healthy wood, and been free from the bad consequences of blight.

Mr. John Mearns states, that the red and white Antwerp raspberries may be brought to bear abundantly in August, long after the usual crop of raspberries is past, by the following management. In May he removes the young fruit, bearing shoots, from the canes, leaving in some cases one or two eyes, in others, cutting them clean off. Under either plan, they soon produce an abundance of vigorous new shoots, which blossom freely in July.

Mr. Elias Hildyard, gardener to Sir Thomas Frankland, kills the grub which infests his onion beds by trenching the beds in winter, digging in manure at the same time, and leaving them exposed to the frost in a rough state till the time of sowing.

A mode of inducing fertility in a barren Swan’s-egg pear-tree trained upon a wall, is described by the Rev. John Fisher, of Wavenden, in Buckinghamshire. It consists in twisting and breaking down the side shoots of the main branches in such a way, as to make them pendulous without separating them wholly from the parent limb. In a short time a grumous formation takes place where the fracture has occurred, the wound heals, the flow of the sap is moderated, and fruit buds are formed instead of sterile shoots.

Mr. William Mowbray, gardener to the Earl of Mountnorris, states, that the different species of eatable Passifloras which do not generally produce fruit, may be induced to do so abundantly, if the pollen of other species is applied to their stigmas.

Currants are preserved in perfection in the garden of James Webster, Esq., of Westham, by being covered with bunting when the fruit is fully ripe, care being had to unloose the bunting occasionally from the bottom of the bushes, in order to remove the decaying fallen leaves.

X. Report on the Instruments employed in, and on the Plan of a Journal of Meteorological Observations, kept in the garden of the Horticultural Society at Chiswick. [◊]

This and the following paper we propose to notice in detail on a future occasion. [p170]

XI. Journal of Meteorological Observations made in the garden of the Horticultural Society at Chiswick, during the year 1826. By Mr. William Beattie Booth. [◊]

XII. On Orache, its Varieties and Cultivation. By Mr. William Townshend. [◊]

The herb orache was formerly cultivated as a kind of summer spinach; but in this country it has long been expelled from the kitchen garden by other kinds. It is, however, still seen in the gardens of France, where it is commonly called Arroche des jardins, being used in that country, both by itself as a spinach, and mixed with sorrel, the acidity of which it corrects. Seven varieties are described, which do not differ in their qualities, but are distinguished by the colour of their foliage.

XIII. On planting the moist Alluvial Banks of Rivers with Fruit-Trees. By Mr. John Robertson. [◊]

The object of this writer is to show that the low grounds that form the banks of rivers are, of all others, the best adapted for the growth of fruit trees; the alluvial soil of which they are composed, being an intermixture of the richest and most soluble parts of the neighbouring lands, with a portion of animal and vegetable matter, affording an inexhaustible fund of nourishment. In such situations, however, the trees are liable to injury from floods in the winter, unless some means are used of draining off the stagnant water. This is to be effected by digging deep trenches between the rows of trees, casting up the earth from the trenches around the trees on either side, so as to form elevated banks. Such is the practice in Holland, where the western slopes of the dykes are generally covered with fruit-trees, chiefly apples and pears. Mr. Robertson is of opinion, that the banks should be raised, if possible, at least three or four feet above the highest water-mark, and be made eighteen feet broad at the base, and twelve at top; the trenches should be fifteen or sixteen feet wide, admitting the soil to be three or four feet deep.

Upon this plan, it is probable that abundant crops would be obtained; but with regard to the quality of the produce, we suspect it will be quite as indifferent as the apples and pears of the Dutch, which are notorious for their want of flavour.

XIV. On Dahlias. By Mr. William Smith. [◊]

This is an attempt to distinguish by words the best varieties of the Dahlia, and to fix the names of those which are the most worthy of cultivation. Sixty kinds are well described, [p171] arranged in divisions depending upon the size of the plants and the colour of their flowers. We do not propose to analyze this paper, which is far too extensive for our limits; but instead, to throw together a few remarks which are suggested by the subject.

The first fact to which we would call attention has reference to acclimatization. The Dahlia has now been cultivated in Europe with the utmost assiduity for nearly thirty years. During that period millions of plants have been raised from seeds, and under almost every possible variation of climate; and anomalies the most singular, not only in colour, but in general constitution and physiological structure, have been obtained. The colour of the flower has been altered from pale yellow, or lilac, to every hue of red, purple, or yellow, to pure scarlet and to deepest morone, or has even been wholly discharged from the radial florets in the white varieties; the period of flowering has been accelerated nearly two months; the tall rank weed, exceeding the human standard in height, has been reduced to a trim bush, emulating the pæony in dwarfishness; the yellow inconspicuous florets of the disk have been expelled to make room for the showy deep-coloured florets of the ray; what is more remarkable still, the same yellow inconspicuous florets of the disk have been enlarged, and stained with rich morone, so as to rival the colours of the ray without losing their own peculiarity of form; and finally, the whole foliage and bearing of the plant has been altered by the substitution of simple leaves for compound ones. But notwithstanding all this proneness to change, notwithstanding the multitude of varieties which have been thus procured by seed, not one individual has yet been discovered, in any degree whatever, more hardy than its ancestors. The earliest frosts destroyed the Dahlias as certainly in 1826, as they could have done in 1789.

But, however strong may be the disposition of the Dahlia to vary from its original structure, it is curious to observe how strictly it conforms to the laws by which such variations are controlled by nature. In altered structure all the changes take place from circumference to centre. The florets of the ray displace those of the disk, but the latter never attempt to occupy the ray; when a change occurs among the florets of the disk, they merely dilate and assume the colour of the ray, without changing their position or their peculiar form. So with the leaves; by a reduction of the lateral leaflet, till the terminal one only remains, simple foliage is substituted for that which was compound: but no case has been found in [p172] which the suppression of the terminal leaflet has taken place and the lateral ones have been preserved. In change of colour, too, there is a circumstance which demands consideration, and of which no explanation has yet been offered. It is not generally known, although long ago noticed by M. De Candolle, that among flowers, yellows will not produce blues, nor blues yellows, although both these primitive colours will sport into almost every other hue. Thus the hyacinth, the natural colour of which is blue, will not produce a yellow, for the dull, half-green flowers called yellow hyacinths, are, in our judgment, whites approaching green; the blue crocus will not vary into yellow, nor the yellow into blue; and the ranunculus and the dahlia, the natural colour of both which, notwithstanding the popular belief to the contrary, with respect to the dahlia, is, we believe, yellow, although they are the most sportive of all the flowers of the gardens, varying from pink to scarlet, and deepest shades of purple, have never yet been seen to exhibit any disposition to become blue. This subject offers a most amusing field for investigation, and would well repay the attentive consideration of the philosopher.

XV. On the Cultivation of Camellias in an open Border. By Mr. Joseph Harrison. [◊]

Mr. H. finds that the double red camellia, the double white, and the double striped, will bear an English winter if planted out when about two feet high, having been previously stunted in their growth by repeatedly stopping their leading shoots. For two winters the young plants are to be protected by a wooden screen fixed round them, and covered by a hand-glass, the whole being enveloped in mats; afterwards they require no other protection than to be guarded from heavy snowstorms, and to be assisted by a thick covering of old tan upon the ground in which they grow, to the distance of two or three feet from their stems. If this success has been met with in Yorkshire, what may not be expected in our more southern counties! On the 12th of March of the present year these camellias were not injured by a frost which did considerable damage to the common laurel.

XVI. A Method of growing Crops of Melons on open Borders. By Mr. William Greenshields. [◊]

The sorts fitted for this purpose are the black rock, scarlet rock, green-fleshed, netted and early Cantaloup melons. The method consists of forming a bed, by half filling a shallow [p173] trench with decayed vegetables, and covering them with the exhausted linings of cucumber beds. The young plants are reared for some time under handlights. For full particulars of this practice, we must refer to the paper itself, which is clearly written, and, coming as it does from one of our most skilful gardeners, well worthy of attention.

XVII. Notice of Five Varieties of Pears received from Jersey in the year 1826. By John Lindley, Esq. [◊]

The fruits here described are of the highest excellence. They are, 1. the Marie Louise; 2. the Duchesse d’Angoulême; 3. the Doyenné gris; 4. the Doyenné panaché; 5. the Beurré d’Aremberg; and 6. the Gloux morceaux. The second, the fifth, and the sixth kinds are represented in two very beautiful coloured plates; and are, perhaps, the most exquisitely flavoured of all the varieties of the pear. The Beurré d’Aremberg and Gloux morceaux are long keepers; the others are autumnal kinds. Of the former it is said, “the flesh is whitish, firm, very juicy, dissolves in the mouth, and is wholly destitute of grittiness; it is sweet, rich, and so peculiarly high flavoured, that I know no pear that can be compared with it in that respect.”

XVIII. Upon the Culture of the Prunus Pseudo-cerasus, or Chinese Cherry. By Thomas Andrew Knight, Esq. [◊]

This species of cherry is expected to become an acquisition of considerable value, for the purpose of forcing; and also as an early fruit, when trained upon an open wall. Mr. Knight recommends its propagation by cuttings, which root freely, and that it be abundantly supplied with liquid manure. From its highly excitable habits, he suspects it to be a native of a cold climate, probably of Tartary.

XIX. On the Culture of the Pine-Apple. By Mr. James Dall.

XX. On forcing Asparagus. By the same. [◊]

These two papers were communicated by the Cambridge Horticultural Society, having gained one of the annual silver medals presented by the London to Provincial Societies. They contain good practical directions for the cultivation upon which they treat.

XXI. Observations upon forcing Garden Rhubarb. By Mr. William Stothard. [◊]

This plan is perhaps the best that can be followed, as it is at once the most certain and the most simple. You sow rhubarb seed on a rich moist border in the beginning of April, [p174] The young plants are well thinned during the summer; in the end of October they are very carefully transplanted into forcing-pots, five or six in each pot. They are placed in a north aspect, to recover the effect of their removal from the seed-bed, and in a month they are fit for forcing. We can safely recommend this method.

XXII. Account of some remarkable Holly Hedges and Trees in Scotland. By Joseph Sabine, Esq. [◊]

This is in elaborate account of extraordinary specimens of hollies, and appears to have been written with a view to induce the more general cultivation in this country of that very valuable tree. At Tynningham, the residence of the Earl of Harrington, are hedges extending to no less a distance than 2952 yards, in some cases thirteen feet broad, and twenty-five feet high. The age of these hedges is something more than a century. At the same place are individual trees of a size quite unknown in these southern districts. One tree measured five feet three inches in circumference at three feet from the ground; the stem is clear of branches to the height of fourteen feet, and the total height of the tree is fifty-four feet. The other places at which the hollies are of unusual size, are Colinton-house the seat of Sir William Forbes; Moredun, the seat of David Anderson, Esq.; Hopetoun-house, the seat of the Earl of Hopetoun, and Gordon-castle, where are several large groups of hollies, apparently planted by the hand of Nature.

XXIII. An Account of a Plan of Heating Stoves by means of Hot Water, employed in the Garden of Anthony Bacon, Esq. [◊]

We conceive that a new æra in horticulture will commence with the publication of this paper. We already possessed contrivances of a sufficiently good kind for all purposes connected with artificial climate, except the power of commanding heat; for which the two methods hitherto employed have been either too clumsy or too costly, and in either case liable to numerous objections. The old mode of introducing heat into a stove, by means of brick flues, has long been considered so bad, that every scheme that promised to supersede such flues has been hailed with joy; the uncertainty of the quantity of heat given out by a brick flue, its continual liability to explosion, the impossibility of preventing the escape of smoke from between the joints of the bricks, are all evils that require a remedy. For this purpose steam was introduced, and with great advantage in extensive ranges of hothouses. But the enormous expense of erecting a steam [p175] apparatus, the danger attending its use in the charge of an unskilful or careless gardener, and also the rapid loss of heat from the pipes upon any neglect of the boiler, have all contributed to prevent the use of steam becoming very general. The plan now described has the great merit of possessing all the good qualities of steam, without any of its objectionable accompaniments; its cost cannot in any considerable degree exceed that of flues, and its effects are so certain and durable, that a house so heated may be almost said to be beyond the power of neglect on the part of the gardener.

Without entering into the details of this plan, for which we must refer to the paper itself, we shall content ourselves with explaining its principle. Suppose two iron reservoirs, A and B, of equal capacity, placed twenty feet apart, and connected at the top and the bottom by iron pipes, the level of both reservoirs being the same; it is obvious that water poured into one of these reservoirs will flow into the other through the connecting pipes, and that it will consequently stand at the same height in both. Let the reservoirs be thus filled above the level of the uppermost pipe, and heat be applied to the bottom of one reservoir, A; the water in this will presently be forced through the upper pipe into the reservoir, B, of water not heated; in proportion as the heated water flows out of A, through the upper pipe, the cold water will flow out of B through the lower pipe; and by this means a circulation of water heated and water to be heated will be formed, which will continue as long as the application of fire to the bottom of one reservoir is continued. When it is discontinued, the temperature of the two reservoirs and of the intermediate pipes will be the same within three or four degrees. As it is the property of heated water to part with its heat very slowly, it follows that heat will continue to be disengaged from the reservoirs and pipes long after the application of fire has ceased. In fact, when the two reservoirs are once heated, the gardener may make up his fires and retire to rest, certain that his house is sufficiently provided with heat for the night.

The paper is accompanied with a plan of a vinery warmed upon this principle. [p176]

---

On the Recent Elucidations of early Egyptian History. [◊]

SINCE the commencement of the present century, the researches of philologists have ascertained that the language of ancient Egypt,—the language of the hieroglyphical inscriptions engraven on its ancient temples and monuments, and of the still existing manuscripts of the same period,—differs from the modern Egyptian or Coptic, only in the mixture in the latter of many Greek and Arabian and a smaller portion of Latin words, introduced during the successive dominion of the Greeks, the Romans, and the Arabs, and occasionally substituted for the corresponding native words. The grammatical construction of the language has remained the same at all periods of its employment: and it finally ceased to be a spoken language towards the middle of the seventeenth century, when it was replaced by the Arabian.

In writing their language, the ancient Egyptians employed three different kinds of characters. First, figurative; or representations of the objects themselves. Second, symbolic; or representations of certain physical or material objects, expressing metaphorically, or conventionally, certain ideas; such as, a people obedient to their king, figured, metaphorically, by a bee; the universe, conventionally, by a beetle. Third, phonetic, or representative of sounds; that is to say, strictly alphabetical characters. The phonetic signs were also portraits of physical and material objects; and each stood for the initial sound of the word in the Egyptian language which expressed the object pourtrayed: thus a lion was the sound L, because a lion was called Labo; and a hand a T, because a hand was called Tot. The form in which these objects were presented, when employed as phonetic characters, was conventional, and definite to distinguish them from the same objects used either figuratively or symbolically; thus, the conventional form of the phonetic T was the hand open and outstretched; in any other form the hand would either be a figurative, or a symbolic sign. The number of distinct characters employed as phonetic signs appears to have been about 120; consequently many were homophones, or having the same signification. The three kinds of characters were used indiscriminately in the same writing, [p177] and occasionally in the composition of the same word. The formal Egyptian writing, therefore, such as we see it still existing on the monuments of the country, was a series of portraits of physical and material objects, of which a small proportion had a symbolic meaning, a still smaller proportion a figurative meaning, but the great body were phonetic or alphabetical signs: and to these portraits, sculptured or painted with sufficient fidelity to leave no doubt of the object represented, the name of hieroglyphics, or sacred characters, has been attached from their earliest historic notice.

The manuscripts of the same ancient period make us acquainted with two other forms of writing practised by the ancient Egyptians, both apparently distinct from the hieroglyphic, but which, on careful examination, are found to be its immediate derivatives; every hieroglyphic having its corresponding sign in the hieratic, or writing of the priests, in which the funeral rituals, forming a large portion of the manuscripts, are principally composed; and in the demotic, called also the enchorial, which was employed for all more ordinary and popular usages. The characters of the hieratic are for the most part obvious running imitations, or abridgments of the corresponding hieroglyphics; but in the demotic, which is still further removed from the original type, the derivation is less frequently and less obviously traceable. In the hieratic, fewer figurative or symbolic signs are employed than in the hieroglyphic; their absence being supplied by means of the phonetic or alphabetical characters, the words being spelt instead of figured; and this is still more the case in the demotic, which is, in consequence, almost entirely alphabetical.

After the conversion of the Egyptians to Christianity, the ancient mode of writing their language fell into disuse; and an alphabet was adopted in substitution, consisting of the twenty-five Greek letters, with six additional signs expressing articulations and aspirations unknown to the Greeks, the characters for which were retained from the demotic. This is the Coptic alphabet, in which the Egyptian appears as a written language in the Coptic books and manuscripts preserved in our libraries; and in which, consequently, the language of the inscriptions on the monuments may be studied. [p178]

The original mode in which the language was written having thus fallen into disuse, it happened, at length, that the signification of the characters, and even the nature of the system of writing which they formed, became entirely lost; such notices on the subject as existed in the early historians being either too imperfect, or appearing too vague, to furnish a clue, although frequently and carefully studied for the purpose. The repossession of this knowledge will form, in literary history, one of the most remarkable distinctions, if not the principal, of the age in which we live. It is due primarily to the discovery by the French, during their possession of Egypt, of the since well-known monument called the Rosetta Stone, which, on their defeat and expulsion by the British troops, remained in the hands of the victors, was conveyed to England, and deposited in the British Museum. On this monument the same inscription is repeated in the Greek and in the Egyptian language, being written in the latter both in hieroglyphics and in the demotic or enchorial character. The words Ptolemy and Cleopatra, written in hieroglyphics, and recognized by means of the corresponding Greek of the Rosetta inscription, and by a Greek inscription on the base of an obelisk at Philæ, gave the phonetic characters of the letters which form those words: by their means the names were discovered, in hieroglyphic writing, on other monuments of all the Grecian kings and Grecian queens of Egypt, and of fourteen of the Roman emperors ending with Commodus; and by the comparison of these names one with another, the value of all the phonetic characters was finally ascertained.

The hieroglyphic alphabet thus made out has been subsequently applied to the elucidation of the earlier periods of Egyptian history, particularly in tracing the reigns and the succession of the Pharaohs, those native princes who governed Egypt at the period of its splendour; when its monarchy was the most powerful among the nations of the earth; its people the most advanced in learning, and in the cultivation of the arts and sciences; and which has left, as its memorials, constructions more nearly approaching to imperishable, than any other of the works of man, which have been the wonder of every succeeding people, and which are now serving to re-establish, at the expiration of above 3000 years, the details of [p179] its long-forgotten history. To trace these stupendous monuments of art to their respective founders, and thus to fix, approximatively, at least, the epoch of their first existence, is a consequence of the restoration of the knowledge of the alphabet and the language of the inscriptions engraven on them. We propose to review, briefly as our limits require, the principal and most important facts that have thus recently been made known in regard to those early times; and shall deem ourselves most fortunate if we can impart to our readers but a small portion of the interest which we have ourselves derived in watching their progressive discovery.

The following are the authors to whom we are chiefly indebted for the few particulars we know of early Egyptian history. Herodotus and Diodorus Siculus, Grecians, and foreigners in Egypt. Manetho, a native; and Eratosthenes, by birth a Cyrenean, a province bordering on Egypt, both residents. Josephus, a Jew, and Africanus, Eusebius, and Syncellus, Christians, Greek authors. Herodotus visited Egypt four centuries and a half before Christ, and within a century after its conquest by the Persians. In his relation of the affairs of the Greeks and Persians, he has introduced incidentally a sketch of the early history of Egypt, such as he learnt it from popular tradition, and from information obtained from the priests. It is, however, merely a sketch, particularly of the earlier times; and is further recorded by Josephus to have been censured by Manetho for its incorrectness. Diodorus is also understood to have visited Egypt about half a century before Christ; and from him we have a similar sketch to that of Herodotus; a record of the names of the most distinguished kings, and for what they were distinguished; but with intervals, of many generations and of uncertain duration, passed without notice. Manetho was a priest of Heliopolis in Lower Egypt, a city of the first rank amongst the sacred cities of ancient Egypt, and long the resort of foreigners as the seat of learning and knowledge. He lived in the reign of Ptolemy Philadelphus, two centuries and a half before Christ, and wrote, by order of that prince, the history of his own country in the Greek language, translating it, as he states himself, out of the sacred records. His work is, most unfortunately, lost; but the fragments which have been preserved to us, by the writings [p180] of Josephus in the first century of the Christian æra, and by the Greek authors above named of the third and fourth centuries, contain matter, which, if entitled to confidence, is of the highest historical value, viz., a chronological list of the successive rulers of Egypt, from the first foundation of monarchy, to Alexander of Macedon, who succeeded the Persians. This list is divided into thirty dynasties, not all of separate families; a memorable reign appearing in some instances to commence a new dynasty, although happening in the regular succession. It originally contained the length of reign as well as the name of every king; but in consequence of successive transcriptions, variations have crept in, and some few omissions also occur in the record, as it has reached us through the medium of different authors. The chronology of Manetho, adopted with confidence by some, and rejected with equal confidence by others,—his name and his information not being even noticed by some of the modern systematic writers on Egyptian history,—has received the most unquestionable and decisive testimony of its general fidelity by the interpretation of the hieroglyphic inscriptions on the existing monuments: so much so, that by the accordance of the facts attested by these monuments with the record of the historian, we have reason to expect the entire restoration of the annals of the Egyptian monarchy antecedent to the Persian conquest, and which, indeed, is already accomplished in part.

Before we pursue this part of our subject, we must conclude our brief review of the original authorities in early Egyptian history, by a notice of Eratosthenes. He was keeper of the Alexandrian library in the reign of Ptolemy Evergetes, the successor to Ptolemy Philadelphus, under whose reign Manetho wrote. Amongst the few fragments of his works, which have reached us transmitted through the Greek historians, is a catalogue of thirty-eight kings of Thebes, commencing with Menes, (who is mentioned by the other authorities also as the first monarch of Egypt,) and occupying by their successive reigns 1055 years. These names are stated to have been compiled from original records existing at Thebes, which city Eratosthenes visited expressly to consult them. The names of the two first kings in his catalogue are the same with the names of the two first kings of the first dynasty of Manetho; but the [p181] remainder of the catalogue presents no further accordance, either in the names or in the duration of the reigns.

To return to Manetho:—amongst the monarchs of the original Egyptian race there was one named by him Amenophis, (the eighth king of the eighteenth dynasty,) of whom it is stated, in a note of Manetho’s preserved by Syncellus, that he was the Egyptian king whom the Greeks called Memnon. The statue of Memnon at Thebes, celebrated through all antiquity for the melodious sounds which it was said to render at sunrise, is identified in the present day by a multitude of Greek inscriptions; one of which, in particular, records the attestation of Publius Balbinus, who visited the ruins of Thebes in the suite of the empress the wife of Adrian, to his having himself heard the “divine sounds of Memnon or Phamenoph;” which latter name is Amenophis, with the Egyptian masculine article φ prefixed, and omitting the Greek termination. The hieroglyphics carved on the statue, and coeval with its date, had been very carefully copied by the French whilst in possession of Egypt, and were engraved in the splendid work, the Description de l’Egypte, to which their researches had given rise. These hieroglyphics contain the alphabetic characters Amnf (being the initial vowel and all the consonants of the name Amenof) inclosed within a ring; a distinction which had been previously observed to take place with the names of the Roman emperors, and of the Grecian kings and queens; and as the rings have hitherto been found to occur in no other instance whatsoever than when containing the names and titles of sovereigns, they are regarded as characteristic signs. It should be remarked, that in the hieroglyphic writing, as in the languages of other eastern nations most nearly connected with Egypt, the vowels are often omitted, and when expressed, have not always a fixed sound. The coincidence of the reading of the hieroglyphic name with that recorded by Manetho, and with the Greek inscription on the statue itself, was so far confirmatory of Manetho’s authority; it was also highly interesting in the evidence it afforded of the employment of the same hieroglyphic alphabet, that was in after use in the times of the Ptolemies and the Cæsars, even in the very early periods of the Egyptian monarchy; for the reign of Amenophis was in the dynasty preceding that of Sesostris: it also indicated the further [p182] advantage to be gained by the application of the alphabet in decyphering other proper names, distinguished by being inclosed in rings, existing on other statues, and in the more ancient temples generally. Considerable progress had been made in reading these, which in several instances had been found to correspond with the names of the kings of the same and of subsequent dynasties to Amenophis, as given by Manetho, when a most important discovery was made of the existence of a genealogical record, in hieroglyphics, of the titles of thirty-nine kings anterior to Sesostris, chronologically arranged. We have already noticed that the names and titles of kings were distinguished by being inclosed in rings; the ring containing the proper name being accompanied usually by a second, inclosing certain other hieroglyphics, expressing the title by which that particular king was designated; and it appears probable that the kings of Egypt were distinguished by their titles rather than by their names, since the same name recurs frequently in different individuals, but the titles are all dissimilar; with a single exception amongst the very many that have come under observation, and in which the same title is common to two brothers. The signification of the titles is yet obscure, except that they are of the same general nature as is frequent in the East, such as “Sun of the Universe,” &c.; but for the purpose of individualizing, the sign is to us of the same value as the thing signified; and as other monuments furnish the names in connexion with the titles, we are enabled to compare the succession evidenced by the titles with the record of the historian, and thus to test the fidelity of the record. The discovery of this hieroglyphic table was made by Mr. William Banks in 1818, in excavating for the purpose of obtaining an accurate ground-plan of the ruins of Abydus, near Thebes. On a side wall of one of the innermost apartments, hieroglyphics were sculptured inclosed in rings, ranged symmetrically in three horizontal rows, each row having originally contained twenty rings, of which twelve of the upper row, eighteen of the middle, and fourteen of the lower row were still remaining, the others having been destroyed by the breaking down of the wall. The hieroglyphics having been copied and lithographed, it was speedily recognised that the rings in the two upper rows consisted of titles only; with the exception of one [p183] proper name, the last of the second row, since known to be the name of the king whose title is the last in the succession, and who was the fourth in reign and generation before Sesostris. The third row was recognised to consist of one proper name and one title, each repeated ten times, and alternating with each other: these are since known to be the name and title of Sesostris, to whose reign the construction of the table is with much probability ascribed. The titles in the same row with that of the ancestor of Sesostris and preceding it, have been identified on other monuments, coupled with names which are those of the predecessors of the same king in the list of Manetho.

It would exceed our limits, and it is not our purpose, to trace in detail the successive steps by which the existence of each of the kings of Manetho’s list, from the expulsion of the Phœnician shepherds from Lower Egypt, and the consequent union of Upper and Lower Egypt in a single monarchy, to the reign of Sesostris, has been attested by the monuments. Suffice it to say, that the same number of individuals as stated by Manetho, namely, eighteen, filling a space of four centuries, are shown, by the monuments, to have reigned in that interval, and to have borne the same relationship, as well as succession, to each other, as is expressed by the historian: that, of the eighteen names, eight in different parts of the list are read on the monuments identically as in the historical record; and that in regard to the names that are not identical, we have the testimony of Manetho that some amongst the kings, Sesostris, for example, were known by two and even by more names. The table of Abydus appears to have been strictly a genealogical record; a record of generations, in which view it is strictly accordant with the historian.

The period of the Egyptian annals on which this light has been thrown, is precisely that which might have been selected in the whole history of Egypt as the most desirable for such purpose. Independently of its very high antiquity, it was the period of the greatest splendour and power of the native Egyptian monarchy, and of the highest (Egyptian) cultivation of the arts. The greater part of the more ancient, and by far the most admirable in execution, of the temples, palaces, and statues, which still attest by their ruins their former magnificence, are the work of that age; and the hieroglyphic inscriptions still [p184] extant on them, and which, when not defaced by wanton injury, are almost as perfect as when first executed, make known the reigns in which they were respectively constructed, and frequently the purposes for which they were designed. This is in itself no small achievement, when we reflect that these extraordinary remains of ancient art were equally the objects of vague wonderment in the times of the Roman emperors, as they were in those of the generation preceding ourselves; but that they are become to us objects of a more enlightened curiosity, which they promise amply to repay, when the study that has already made known their founders, shall reveal the signification of the hieroglyphic histories, with which the walls of the palaces and temples are covered. Already have we gained some very important facts in regard to the condition, political and otherwise, of the countries adjoining to Egypt at that early period. The monuments of Nubia are covered with hieroglyphics, perfectly similar both in form and disposition to those on the edifices at Thebes; the same elements, the same formulæ, the same language; and the names of the kings who elevated the most ancient amongst them, are those of the princes who constructed the most ancient parts of the palace of Karnac at Thebes. As far as Soleb on the Nile, 100 leagues to the south of Philæ the extreme frontier of Egypt, are found constructions bearing the inscriptions of an Egyptian king; evidencing that, during the period of which we have been treating, Nubia was inhabited by a people having the same language, the same belief, and the same kings as Egypt. To the south of Soleb, and for more than 100 leagues in ascending the Nile, in ancient Ethiopia, very recent travellers have discovered the remains of temples, of the same general style of architecture as those of Nubia and Egypt, decorated in the same manner with hieroglyphics representing the same mythology, and analogous to those of Egypt in the titles, and in the mode of representing the names and titles, of the sovereigns. But the proper names of the kings inscribed on the edifices of Ethiopia in phonetic characters, have nothing in common with the proper names of the Egyptian kings in the dynasties of Manetho; nor is one of the Ethiopian names found either on the monuments of Nubia or of Egypt. Thus there was a time when the civilized part of Ethiopia,—Meroe, and the banks [p185] of the Nile between Dongola and Meroe,—were inhabited by a people having language, writing, religion, and arts similar to Egypt; but, in political dominion, independent of that country, and ruled by kings of whom it does not appear that any historical record whatsoever has come down to us.

The dates of the expulsion of the Phœnican shepherds from Egypt, and of the reign of Sesostris, in years of the æra of our computation, have been favourite subjects of discussion with chronologists: Archbishop Usher fixed the former of these events in the year B. C. 1825; which would make the commencement of the reign of Sesostris about B. C. 1483. The reign of Sesostris is connected with the early Grecian chronology by the migration of Danaus, brother of Sesostris, who, according to the Parian marbles, arrived in Greece in 1485, which is a very few years earlier than the dates of Usher would assign to that event. M. Champollion Figeac, brother of the M. Champollion to whom the greater part of the discoveries made by the interpretation of hieroglyphics are owing, himself a distinguished chronologist, has assigned the year B.C. 1822 to the expulsion of the Phœnicians, which Usher had placed in 1825: the date of M. Champollion being derived from Manetho’s statement, that the Phœnician invasion took place in the 700th year of the Sothiacal period, viz., B.C. 2082, and that their dominion in Egypt continued 260 years. Historical accuracy may make it desirable, that the exact year of the most ancient as well as of more modern events should be determined, if it be possible: but for purposes of general interest, and especially for comparison with the chronology of cotemporary nations, which at that early period is in every case more unsettled than the Egyptian, the period seems sufficiently determined. The date before Christ 1822, pursued downwards through the dynasties of Manetho, conducts with very close approximation to the known period B.C. 525 of the conquest of Egypt by the Persians; and intermediately, accords very satisfactorily with the dates, according to the Bible chronology, of the conquest of Jerusalem in the reign of Jeroboam by Shishak, king of Egypt, and of Tirhakah, king of Ethiopia and Egypt, who made war against Sennacherib; these are the Sesonchis of Manetho, and Sh.sh.n.k of hieroglyphic inscriptions on a temple at Bubaste, and on one of the courts of the [p186] palace at Karnac,—and the Taracus of Manetho, and T.h.r.k of hieroglyphic inscriptions existing in Ethiopia and in Egypt[33].

In respect to the connexion of the events of the Jewish and Egyptian histories, the period between the expulsion of the Phœnicians and the reign of Sesostris possesses a peculiar interest, as being that of the residence of the Israelites in Egypt, and of the Exodus. In the history of Josephus, we have an extract from Manetho, in which this latter event is expressly stated to have taken place under the father of Sesostris, a king whose name, in Manetho’s list, is Amenophis, (the third of that name,) and on the monuments Ramses. The date which chronologists are generally agreed in assigning to the Exodus is 1491; that of the termination of the reign of Amenophis, according to Champollion, is 1473, or, if the correction of his chronology which we have suggested in a note be just, 1478: it is singular that the difference of thirteen years (between 1491 and 1478) should be precisely the duration of a very suspicious interval which Manetho states to have taken place, after Amenophis had gone with his army in pursuit of the Israelites; and during which interval neither the king nor his army returned to [p187] Egypt, but are stated to have been absent in Ethiopia. If the Exodus occurred during the reign of any of the kings of the eighteenth dynasty, it could only have been in the reign of the immediate predecessor of Sesostris; since his conquests in Phœnicia, and his expeditions against the Assyrians and Medes, must have brought him in contact with the Israelites, had they been then residing in the Holy Land, so as at least to have caused some mention to have been made in their history of the passages of so great a conqueror. But presuming Amenophis, father and predecessor of Sesostris, to have been the Pharaoh of the Exodus, the wandering of the Israelites in the desert for forty of the fifty-five years ascribed to the reign of Sesostris, is a sufficient explanation of his being unnoticed in the Jewish history; whilst the fact of that nation having been subject to the Egyptians during the reign of Ousirei, commencing 124 years before the death of Amenophis, is attested by the paintings on the wall of one of the chambers of the tomb of that king, discovered by Belzoni, and with which we are so well acquainted by means of the model exhibited in England.

Whilst recalling to recollection the peculiar physiognomy of the Jews pourtrayed in that tomb,—and which is as characteristic of their present physiognomy as if it had been painted in the present age, instead of above 3000 years ago,—the equally well characterized, but very different physiognomy of the Phœnician shepherds, represented on the monuments of the same period, is decisive of the error of Josephus, who imagined the Jews and the Shepherds to be the same people. The Phœnician shepherds, long the inveterate enemy of the Egyptians, form a leading feature as captives, in the representations of the exploits of the monarchs who conducted the warfare against them. These people are always painted with blue eyes and light hair; and it is not a little curious to see assembled on the wall of the same apartment, different races, so distinctly characterised as the Jew, the Phœnician, the Egyptian, and the Negro; the latter in colour, and in the outline of the features, in painting and in sculpture, precisely as at present; all, moreover, inhabitants of countries not very distant from each other, and at a period when not more than twelve or thirteen centuries had passed since all these races had descended from a single parent. In the writings which attempt to explain from natural causes [p188] the diversity of race amongst mankind, much power has been ascribed to the effects of time and climate: but the facts with which we are now becoming better acquainted than before, do not appear to admit of explanation from those circumstances. It is worthy of notice that the negro, and the light-haired and blue-eyed people, the two races who might be deemed at the greatest distance apart amongst the varieties of man, are, equally with the intermediate Egyptians, the descendants of Ham.

Of the succession of kings in Manetho’s chronology, from Sesostris to the Persian conquest, a space of nine centuries and a half, about one half the names have been already identified on different monuments: four of the Persian monarchs, subsequent to the conquest, have also been traced in inscriptions in phonetic characters; their names are written, as nearly as can be spelt with our letters, Kamboth, (Cambyses); Ntariousch, (Darius); Khschearscha, (Xerxes); and Artakschessch, (Artaxerxes.)

The ascent by monumental evidence to yet more remote antiquity than the expulsion of the Phœnician shepherds, (B.C. 1822), is not altogether without hope, notwithstanding the general demolition of the temples of the gods, which took place according to Manetho, during the long dominion of the Phœnicians in Egypt. We learn from the Description de l’Egypte that even the most ancient structures at Thebes are themselves composed of the debris of still more ancient buildings, used as simple materials, on which previously sculptured and painted hieroglyphics are still existing; these are doubtless the remains of the demolished temples, but the inscriptions will require to be studied on the spot. There is also reason to believe, that there exists amongst the ruins of the palace of Karnac, a portion of still more ancient construction than the palace itself; which, having escaped demolition, was incorporated with the more recent building. The inscriptions on this apparently very ancient ruin present the name and title of a king, which form a very interesting subject for future elucidation. The title does not accord with any one now extant on the table of Abydus, but possibly may have been one of those which were destroyed with a portion of the wall, and which are of kings of earlier date than the expulsion of the shepherds. The name is Mandouei, which name occurs in the dynasty anterior to Sesostris, but coupled [p189] with a different title, an effectual distinction; nor does the name recur in any subsequent dynasty. M. Champollion Figeac has, with much ingenuity, shown the probability of the identity of the Mandouei of the ancient ruin with the Osymandyas, Ousi-Mandouei, mentioned by Diodorus Siculus as an Egyptian king greatly distinguished by his conquests, whose reign M. Champollion infers, from the historical passages relating to him, to have commenced 190 years before the Phœnician invasion, or B.C. 2272 years; a prodigious antiquity, and of the very highest interest should it be established, since there exist of this individual no less than three statues in European collections, distinguished by the same name and title: two of these are colossal, one at Turin, and a second at Rome: a third is in the British Museum; and as all particulars must interest which relate to a statue, of which there is at least probability that is the most ancient existing in the world,—the date attributed to it being earlier than the birth of Abraham,—we copy from Burckhardt the following short description of its discovery: “Within the inclosure of the interior part of the temple at Karnac, Belzoni found a statue of a hard, large-grained sandstone: a whole length naked figure sitting upon a chair with a ram’s head upon the knees: the face and body entire; with plaited hair falling down to the shoulders. This is one of the first, I should say, the first Egyptian statue I have seen: the expression of the face is exquisite, and I believe it to be a portrait.”—(J. L. BURCKHARDT, Travels in Nubia, lxxvii. Letter to Mr. W. Hamilton, 20th February, 1817.)—This statue is in the farthest corner on the right hand side after entering the gallery of the Egyptian antiquities in the British Museum; and compared with other statues in the same gallery, which are of kings of the eighteenth dynasty, the dissimilarity of the features from the very characteristic ones of the latter family is too striking to be questioned. The problem of the age of this king Mandouei is, at all events, a highly curious one; and will probably receive its solution amongst the many other valuable discoveries which cannot fail to result from M. Champollion’s projected visit to Egypt, in which he will be accompanied by the sincere good wishes of every one in every country, who feels an interest in the restoration of authentic history. E. S.

[33] It appears to us that a slight inaccuracy has crept into the deduction of all the dates in M. Champollion’s Chronology subsequent to the expulsion of the shepherds. The date of that event is the foundation of the subsequent dates, and is supposed to have taken place B.C. 1822; after which, according to the extract of Manetho in Josephus cited by M. Champollion, Thoutmosis, the king by whom they had been expelled, reigned 25 years and 4 months, followed by the other kings of the eighteenth dynasty, making altogether 342 years and 9 months: (including the 2 years and 2 months additional of Horus, in compliance with the version of the passage in the Armenian text of the Chronicle of Eusebius.) This number, 342 years and 9 months, falling short of the 348 years attributed to the eighteenth dynasty in Eusebius and Syncellus, M. Champollion has suggested that Thoutmosis may have reigned the five years which constitute the difference, before the expulsion of the shepherds, since, according to the record, he did reign, some years before that event, over all the parts of Egypt not possessed by the shepherds. So far, so well: but in such case, the year B.C. 1822, being the epoch of the expulsion of the shepherds, and not of the commencement of the eighteenth dynasty, must surely correspond to the fifth year of the reign of Thoutmosis, and not to the first, as M. Champollion makes it. We have hesitated to venture this remark on a matter to which M. Champollion must have given much attention, believing that mistake in us is much more probable than an accidental inadvertence in him; but we have returned frequently to the consideration, without having been able to satisfy ourselves; and the rectification of our mistake, if it is one, may prevent others falling into the same. [p190]

Proceedings of the Horticultural Society. [◊]

June 19th.

AT this meeting a paper was read from the President, T. A. Knight, Esq., upon the culture of the mango and cherimoyer. Its object was to suggest some improvements in the management of these and other trees cultivated in stoves, deduced from an application of Dutrochet’s electrical theory of vegetation to practice. It has now become generally known that this observer is of opinion that the motion of the fluids in plants depends upon two currents of electricity, setting with very unequal force between the denser fluid of the tree and the lighter fluid of the soil in which the tree is planted; the more powerful current setting from the latter to the former, and so producing absorption, by conveying aqueous particles into the roots, through the vegetable membrane of the epidermis. In applying this theory to practical purposes, Mr. Knight recommends that the pot in which the cherimoyer or mango is planted, should itself be surrounded by a medium through which an equable and regular supply of fluid may be conveyed to the roots, and that the naked surface of the pot should by no means be exposed to the free action of the atmosphere. Without entering upon any question of the accuracy of the French philosopher’s observations, it is quite certain that such a mode of cultivation is that which is most congenial to plants, and which is indispensable to those of a habit at all delicate. The common practice of plunging pots into a tan-bed, or among sand, if in glass-houses, or in the earth if in open borders, is a proof of the necessity that gardeners have found, of securing as regular a temperature and degree of humidity as is possible for the outside of their flower-pots; through the pores in which, moisture is chiefly conveyed to the roots, which always cling to the inside surface of the pot.

Specimens of roses produced by branches budded upon the Rosa indica, were exhibited by Alexander Evelyn, Esq. We notice these not only on account of their extraordinary beauty, but also for the sake of recommending most strongly the adoption of the practice where delicate roses are found difficult of cultivation per se. If we consider what happens when the operation of budding, or grafting has succeeded, the reason of the advantage derived from such an operation will be apparent. When a bud of one variety is inserted under the bark of another variety, a union takes place between the cellular substance of the two; the bud is then placed in the same [p191] situation with regard to the stock, as the seed when sown is with regard to the earth. It immediately derives its nutriment from the ascending sap of the new tree, and begins to form its wood and branches, and to secrete its proper juices in proportion to the supply of food it now receives. If a plant from any cause produces roots with difficulty, its whole habit will be delicate, and its flowers if formed, will, as in the case of that most lovely of flowers, the double yellow rose, probably fall off without expanding, from the want of an adequate supply of nutriment from its roots; but, as in all trees, every bud is, when fully formed, in itself a perfect and distinct individual, if such an individual be removed from its own root, and placed where it will be supported by the healthy vigorous roots of another species of variety, which happens in budding, it will no longer have to depend upon a source, the supplies from which are imperfect, but on the contrary, like a seed removed from barren fertile ground, it will flourish in a degree before unknown. The contrary effect takes place when a vigorous plant is transferred to one less vigorous. And hence, the whole effect of stocks upon the scions, or buds inserted upon them.

There was also a great variety of fruit and flowers upon the table, and seeds of several useful vegetables were distributed.

July 3rd.

Seven medals were awarded to different individuals for fruit sent by them to the Society’s fête on the 23rd of June; and one to Capt. Drummond, for his “successful exertions in bringing living plants of the mangosteen from the East Indies.” A paper by the president was read upon an improvement in the mode of constructing hotbeds, but we despair of explaining it successfully without reference to figures. Among the display of fruits and flowers, which were exceedingly numerous, we were particularly struck by a collection of twenty-two varieties of strawberries from the Society’s garden.

Upon this occasion, thirty-nine new members were either ballotted for, or proposed, a striking proof of the estimation in which the Society is held by the public.

July 17th.

Upon this occasion, an enormous pine-cone from the River Columbia was exhibited. It measured 1612 inches in length, and was stated to have been procured by the Society’s collector, Mr. David Douglas. Its seeds were represented to be as large as those of the stone-pine, and eatable. The tree is of the family of Pinus strobus, [p192] and will be an invaluable acquisition to our forests, if it should prove to succeed as well in this climate as in its own. We have already given some account of this plant in the last number of the old series of this Journal. The usual display was made of the finest fruit and flowers of the season.

August 7th.

A complete coloured set of the costly Flora danica was placed upon the table, having been presented by His Majesty the King of Denmark. An improved apparatus for fumigating hothouses was exhibited by its inventor, Mr. John Read: it consists of a brass cylinder, attached to the orifice of a pair of bellows, and fitted up with a chimney and draft-hole closed by a valve. The tobacco is put into the cylinder and ignited, and the blast from the bellows expels the smoke. The contrivance is ingenious enough, but while a hot-house fifty feet long, may be filled with smoke in ten minutes by means of a flower-pot, with a hole in its bottom, and a common pair of bellows, we cannot recommend any more expensive, and certainly less efficient apparatus.

The table was covered with a profusion of fruits and flowers.

August 21st.

The meeting-room this day exhibited a gratifying proof of the excellence of the productions of our English gardens. Of flowers, there were dahlias of the richest colours, and the most varied hues; some produced by plants that retain all their ancient stature, and others by dwarfs which seem to have lost nearly every character of the dahlia but its beauty. Of fruits, there were endless varieties of apricots, apples, pears, peaches, nectarines, grapes, pine-apples, and melons; one of the latter, from the garden of John Fuller, Esq., weighed thirteen pounds. The best apricot was the Moorpark; the best apple, the Duchess of Oldenburg, than which no princess has a fairer bloom, the best pear the Jargonelle, the best peach the Bourdine (forced), the best pine apple the Black Jamaica. We mention these as a guide to our readers, in their purchases of fruit-trees; for it is certain, that no greater service can be rendered to the public, than to point out the means by which they may avoid encumbering themselves with the polyonymous trash with which every nursery abounds. [p193]