Dy’d in the fainting violet away.”
Since the time of this justly celebrated philosopher, it has been objected, that the seven colors above mentioned are not primitive. It seems very obvious that there can be only three primitive colors, namely, red, yellow, and blue; since all the colors can be made by means of these. It has lately been advanced by Prieur, that the primitive colors are violet, green, and red; that the yellow is formed with red and green, the latter being in excess; and that when the red is in excess, they form orange; the green and violet form blue. The colors excited by the different refrangible rays do not appear to determine what are the primitive colors, since we find that different rays are capable of producing the same color, as a mixture of the yellow with the red produces orange. And it must be admitted, that the violet rays excite, in some degree, the idea of red along with the blue; as in the green, the yellow and blue may be discerned, but none of the red. When the different colored rays are mixed together, either by recomposition, or by getting each color by a separate Spectrum, the result will be white light. Hence Sir Isaac Newton concluded, that when the rays are promiscuously reflected from any surface it will appear white. He also found, and the discovery has since been confirmed by the experiments of Dr. Herschell, that the different colored rays have not by any means the same illuminating power. The violet rays appear to have the least luminous effect, the indigo more, the blue a little more, the green very great, between the green and the yellow the greatest of all, the yellow the same as the green, and the red less than the yellow.[44] From experiments it is found, that those rays of light are of the largest quantity that paint the brightest colors; and of all these, the red rays have the least refrangibility. Without light vegetables would have no color, but would appear white; this has been remarkably illustrated by Professor Robison. Some bodies absorb one colored ray, others another, while they reflect the rest. This is the cause of color in bodies. A red body, for instance, reflects the red rays and absorbs the rest. A white body reflects all the rays, and absorbs none; while a black body, on the contrary, absorbs all the rays, and reflects none:[45] this shows, that black colored apparel is very improper during the heat of summer, or in tropical climates.
[There is one difficulty scarcely mentioned, and surely not accounted for, in the preceding chapter: i.e. How are we to reconcile the creation of light on the first day, and the creation of the sun not until the fourth?
This has been a standing proposition since the revival of learning. There can be no doubt but the account of the creation, arrangement and nature of the world, as given by Moses, is correct; and would so appear to the most philosophically scientific, could we ascertain certainly the meaning of the sacred historian, and did we understand perfectly the phenomena of nature.
It is reasonable to suppose that the discoveries in natural philosophy would tend to influence the explanations of Moses’ account. This is the fact. These discoveries have produced two theories in regard to light: The vibratory, or Cartesian; and the corpuscular, or Newtonian.
The Newtonian theory supposes the sun to be the original and principal source of light; and that light is emitted from the sun’s surface in inconceivably small corpuscles, in such rapid succession, and in straight lines, as to seem a continuous ray, though, in reality, the particles are a thousand miles apart in their approach to the earth.
This is the most popular of modern theories, and the only one, as I recollect, employed by commentators in illustrating the account of Moses; or rather in solving the difficulty by reconciling this theory with his account.
Some have supposed the sun was created long before, our earth, and that his beams took effect on our earth, as now, on the fourth day from his creation. Others have supposed that the sun and earth were created simultaneously, but that the sun’s beams did not fully penetrate our atmosphere, so as to make himself distinctly visible as now, until the fourth day. In both these cases it is supposed that the words of Moses, in regard to the creation of the sun on the fourth day, are to be interpreted of his appearance, and influence on the earth, by dispensing light. But this does not account for the existence of light from the first to the fourth day. This is an insuperable objection here.
Finding the foregoing theories pressed with this insurmountable difficulty, other commentators have supposed, Light was a real substance, created simultaneously, and in conjunction with the original chaotic mass of our earth; and when God said “Let there be light, and there was light,” He, by his divine power, caused the chaotic light to separate itself from the earth, and, departing, to condense in the body of the sun; or, as some would probably say, in view of Dr. Herschell’s solar discoveries, in the phosphoric clouds which surround the real body of the sun. In this case, if the light concentrated in the body of the sun, then that luminary must be a body of condensed light: if in the solar phosphoric clouds of Dr. Herschell, then those clouds would be condensed light. This body of condensed light is considered the source of our solar light, which flies off from it in the form of rays or beams.
Dr. Ure, in his Chemical Dictionary, article Light, takes this view. He says, “We learn from scripture, that light pre-existed before this luminary (the sun) and that its subsequent condensation in his orb was a particular act of Almighty Power. The phosphorescence of minerals, buried since the origin of things in the bowels of the earth, coincides strictly with the Mosaic account of the creation. We shall therefore regard light as the first born element of chaos, as an independent essence, universally distributed through the mineral, vegetable, and animal world, capable of being disengaged from its latent state by various natural and artificial operations.”
This theory, as I understand Dr. Ure’s view, has two advantages, and three disadvantages. It accounts for the production of light on the first day, as Moses says. It also accounts for the artificial production of light by friction between bodies which have never been exposed to solar light, by combustion, compression, &c. For though it supposes light “subsequently condensed” in the sun, I presume it does not suppose all the light thus transferred from the earth, and condensed: much of it is latent, and combined with other substances, from which it is evolved by friction, combustion, compression, &c.
But this ingenious theory, which is mentioned by our author, and attributed to Dr. Wall, is pressed with three difficulties:
1. It does not suppose the existence of the sun until the fourth day, and of course no common centre of attraction to the earth and other planets. But it is impossible to conceive of the safe existence of the planets previous to the existence of their common center, which now regulates their order and motion. This is an insuperable difficulty, unless we resort to a “particular act of Almighty Power.”
2. If the body of the sun be “condensed light,” abstracted from the earth, the scene of its creation, then we must suppose that a body more than a million times greater than the earth was drawn off from it, which indeed would require an “act of Almighty Power,” and is utterly irreconcilable to the laws of attraction.
3. This view also destroys the idea of the sun’s being an opake and habitable globe, unless we could conceive the inhabitants capable of dwelling in “condensed light;” which supposition is at variance with all our ideas of rational existence. Hence it robs the mind of the pleasing and almost intuitively correct idea of the sun’s being a habitable globe.
These difficulties appeared so great that others, and particularly Dr. Adam Clarke, have offered a new mode of interpretation, founded on the Newtonian theory as improved by Dr. Herschell. Dr. Clarke supposes that caloric, or latent heat, was produced on the first day, when God said, “let there be light; and there was light.” In this case he considers that latent heat and latent light are, probably, the same: or that it is the same subtile substance diffused throughout creation, which is capable of producing heat and light, when properly excited.
Yet, in his remarks on the sun, he embraces Dr. Herschell’s ideas of the sun’s real body being opake and habitable, surrounded by phosphoric clouds which are the source of our solar light. Of course the Doctor only transfers the source of light from the real body of the sun to these phosphoric clouds with which he is invested. Our solar light then comes by impulsion from these clouds, and not from the sun’s real body.
These clouds are supposed to give light to the Solar inhabitants also, the intensity of which is regulated by a stratum of clouds placed below the outer phosphoric clouds, and which defends the sun’s real body from too great degree of light.
This is Dr. Herschell’s supposition, and seems to be pretty well established.
This ingenious theory solves the difficulty under notice, by supposing that caloric, and not light, is intended in the third verse, where God said, “Let there be light.” And by supposing latent light, as well as latent heat, it seems to provide for the well known existence of light in combination with many, if not all, terrestrial substances; and yet it refers to the sun as the principal source of light, which according to this interpretation, was not necessary to the existence of the substance intended in the third verse—“Let there be light, and there was light.”
This theory has another most excellent suggestion, viz: that the heat excited by the sun at the earth’s surface, is produced by the luminous rays of the sun combining with the caloric in the atmosphere, and other substances at the surface of the earth. This suggestion supposes a very close affinity, if not identity in the matter of light and heat.
Although this explanation approaches much nearer a satisfactory solution of the difficulty in question, yet it is by no means unembarrassed.
In the first place it is built upon a singular translation of a word. The text, according to this theory, should be, “And God said let there be caloric, and there was caloric.” This may be the text; but I cannot help thinking, that a bias to a system of philosophy, and a strong desire to cut the difficulty rather than solve it, suggested this translation. The text seems to have been so generally and uniformly understood of light, it would be difficult to alter it. It would be better to suspect a defect in our knowledge of the source and nature of light.
Again: this view seems to suppose a consecutive creation, which is at variance with a seemingly well settled opinion, in regard to the Solar System, and even at variance with Dr. Clarke’s own remarks on Gen. chap. i, v. 2. On this verse he says: “God seems at first to have created the elementary principles of all things.”
Finally: as his view is Newtonian, it is liable to all the objections to which that theory is liable: such as the diminution which would take place at the source from whence the light came; and the destructive force with which it would fall at the surface of the earth.
These considerations, with others, have influenced many of the most learned and acute philosophers to look for another theory. Our own countryman, Dr. Franklin, felt them. He says, in a letter dated April 23, 1752, in reference to the theory, of light being particles of matter driven off from the sun’s surface; “Must not the smallest portion conceivable have, with such a motion, a force exceeding that of a twenty-four pounder discharged from a cannon? Must not the sun diminish exceedingly by such a waste of matter, and the planets, instead of drawing near to him, as some have feared, recede to greater distances, through the lessoned attraction? Yet these particles with this amazing motion, will not drive before them, or remove the least, and slightest dust they meet with, and the sun appears to continue of his ancient dimensions, and his attendants move in their ancient orbits.”
He then supposes the phenomena of light may be more satisfactorily solved by supposing a subtle fluid, universally diffused, which is invisible when at rest, but becomes visible when put in motion, by affecting the nerves of the eye, as the vibrations of the air affect the ear, and produce the sensation of sound; and that the different degrees of intensity in the vibrations, will account for the different colors. See Nicholson’s Encyclopedia, Light.
This is the vibratory or Cartesian system of light. As already suggested, it supposes the existence of a subtle, luminiferous ether, diffused throughout the universe, pervading every particle of matter, and is capable of being put in motion, so as to become visible, by the sun, as the grand natural excitant, friction, combustion, compression, &c. The laws of the vibrations of this luminiferous fluid, are precisely the same with those ascertained, and determined, in regard to light as commonly understood. This luminiferous fluid is to be considered an elementary substance, and was created when the different substances composing the chaotic mass were created. At its first creation, like caloric, it was in a latent state, as no excitant as yet had put it in motion.
It is to be understood, therefore, that the substances of each planet in the Solar System, as well as the sun himself, were created simultaneously in a chaotic state, at their proper relative distances from each other: that the requisite quantity of each elementary substance was present in each mass: but as caloric, and this luminiferous ether were latent, these masses were solid, frozen lumps; inactive and lifeless; and darkness necessarily prevailed. This then was the original condition of the elements of our Solar System, according to the scriptures. “And the earth was without form and void; and darkness was upon the face of the deep.” Gen. i, 2.
In order, therefore, to produce a quickening in these masses, which rendered them soft, it was only necessary to call the latent caloric, and this luminiferous ether into action, which would agitate, and bring to light the whole mass, and thus commence the arrangement and organization of the Solar System. However, as there was no exciting cause then in operation, it is evident the Almighty must have given the first impulse to these elements. This he did, and the important fact is recorded by Moses in these words: “And the Spirit of God moved upon the face of the great deep,” Jehovah saying at the same time, “Let there be light.”
Here is the Mosaic account of the production of light, and possibly heat also, which took place on the first day. The same process went on simultaneously in the sun and planets, and the continued action cleared up their respective atmospheres, and the sun became visible at the earth’s surface on the fourth day. Hence, the sun was said to have been made on the fourth day.
This solution of the difficulty is consistent with the account of Moses; and also all the well ascertained phenomena of light can be satisfactorily explained by it. It will naturally lead the mind to observe the resemblance between the phenomena of light and heat, and impel us to the conclusion, that light, or vision, is the effect of a material cause, as heat is of caloric: and it is natural to suppose this cause is in the same relation to light, that caloric is to heat. Of course we should conclude that light, or the luminiferous ether in a latent state, enters into combination with all substances, as does caloric; and at the same time a large proportion of it is free, or in motion, and of course sensible to the eye, as free caloric is to the sense of feeling. Moreover we must conclude that this latent light is capable of being set free or evolved by the exciting influence of the sun, as also by friction, compression, combustion, chemical action, &c. It will be of advantage, therefore, to establish the fact of the existence of latent light, in combination with terrestrial substances.
That this is the fact may be proven by a single reflection on the process of combustion. It is a daily observation that light is produced by burning bodies. Let us suppose these bodies burnt at midnight in a close room; still light will be given out copiously and constantly. Whence this light? The natural and obvious answer is, it was in combination in a latent state with the burning bodies, and by combustion it was set free, and thrown out, and thus put the surrounding luminiferous ether in motion.
It is said by some, the light evolved in this case is not from the burning bodies, but from the oxygen which is supplied by the air to support the combustion. This does not alter the case at all: for then the light was in combination with the oxygen, and was invisible, being in a latent state, until it was set free from the oxygen by combustion.
The same conclusion is obtained in the process of compression and expansion. If atmospheric air, or oxygen be suddenly compressed in a glass syringe; or if a glass ball, filled with the latter, be suddenly broke in vacuo, a flash of light is instantly perceived. In this case the light suddenly becomes visible, which was invisible before, being latent in combination with the air. (Ure.)
We arrive at the same conclusion in case of friction. It is well known that pieces of wood can be made to blaze by rubbing them together. But it is not so well known, that two pieces of rock crystal, or quartz, taken from any depth in the earth, and which cannot be supposed to have ever been in the light of the sun, when rubbed quickly together, even under water, will give out volumes of light. Whence this light? from the quartz doubtless. Of course it must have been in a latent state, and was set free by friction. Let it be strictly observed, the crystals never were exposed to the light of the sun, of course could not have derived this light from that luminary.
We must come to the same conclusion, in regard to the light given out by animal substances. Many insects are known to have the power of evolving light, or putting the surrounding luminiferous ether in motion, which is the same. Putrescent animal matter has been observed to possess it, in some cases, in a very great degree; sufficiently to illuminate a room, or pantry, for hours together. In some instances the fingers of those who touched the luminous flesh, became luminous.
This is eminently the case in regard to some fishes. A species of fish called pholas, has the power of evolving a large quantity of light. This power is greater when the fish is sound and fresh. Pliny mentions this fish, and says it rendered the hands and clothes of persons luminous. When put in water, under proper circumstances, it renders the water luminous. But when put in milk, a single pholas made seven ounces of it so luminous as to enable one to distinguish the faces of persons present. Ency. Brit. Art. Light.
The evolution of light from the sea in the night, is a fact of common observation, and is sometimes so great as to enable one to read large print on a ship’s deck. Ency. Brit. Art. Light.
In all the above instances, and many more might be added, the light evolved, or, (which is the same thing in this investigation,) the luminiferous ether put in motion, must have been in a state of combination with the substances from which it was evolved. The only question which remains is this: Was all this light transmitted from the sun, and become latent and combined at the earth’s surface by absorption?
It would certainly be hazardous to answer this question in the affirmative. For how could we account for the evolution of light from those bodies which have never been subject to the sun’s influence?
Again: If all this light had been transmitted from the sun, it will inevitably follow, that there was a time when the quantity of light at the surface of the earth, and in combination with terrestrial bodies, was very small, and of course combustion, friction, and compression of bodies produced anciently a much smaller quantity of light than now; because there was a smaller quantity in combination.
It is evident that this supposition would come to this conclusion: The quantity of light, in combination at the earth’s surface, has increased in the same ratio as the increase of the duration of the influence of the sun on the earth: and, by consequence, the quantity of light produced by artificial means has increased in the same proportion. Of course, fires and candles burn more brightly now than they did five thousand years since.
Though this conclusion is legitimate from the foregoing supposition, yet it is at war with common sense, and the current observations of the world.
We are therefore compelled to conclude that the matter of light is diffused throughout the universe, as is caloric, and that it is evolved, or put in motion by the influence of the sun; as also by artificial and chemical means; as combustion, compression, friction, chemical action, &c.
This conclusion is much strengthened by the fact, that the existence of caloric is well ascertained, not as proceeding from the sun, but in combination with all terrestrial substances; and also by the fact of the constant analogy between the phenomena of light and heat. This analogy is so strong and striking that we are compelled to conclude, if heat be the effect of a real substance, light must be also. Indeed the analogy is so strong that it almost convinces us of the identity of the matter of heat, light, electricity, and galvanism.
Notwithstanding the amount of evidence is against this supposition at present, yet there is a strong tendency in recent philosophical experiments to confirm it; and I am inclined to believe that future discoveries will confirm this identity. Some of the most obvious evidences in favor of it may be introduced here.
1. Almost all the celebrated authors and experimenters have occasionally suggested the probability of this identity. Mr. Turner, Elements of Chemistry, p. 67, says, in reference to heat and light: “It has been supposed that they are modifications of the same agent; and though most persons regard them as independent principles, yet they are certainly allied in a way which at present is inexplicable.” Again, p. 71. “Mr. Leslie conceives that light when absorbed, is converted into heat.” Dr. Henry (Art. Light,) says, “A new fact has been lately ascertained by Dr. Delaroche, which seems to point out a close connection between heat and light, and a gradual passage of the one into the other. The rays of invisible heat pass through glass with difficulty at a temperature below that of boiling water; but they traverse it with a facility always increasing with the temperature, as it approaches the point at which bodies become luminous.” “The general facts, says Sir H. Davy, of the refraction and effects of the solar beam, offer an analogy to the agencies of electricity.” (Ure, Chemical Dictionary, Article Light.) It is well known that this view pressed itself strongly on the attention of Sir Isaac Newton, during his philosophical investigation. See Ure, Chem. Dic. Art. Light.
2. This identity is strongly suggested by the constant and striking analogy between the laws of heat and light.
First: The color of surfaces has an influence on the passage of light and heat.
Secondly: The power of light, heat, and electricity diminishes as the squares of their distances.
Thirdly: The particles of heat, light, and electricity, are idio-repulsive.
Fourthly: The passage of the electric spark is generally attended with the production of light and heat.
Fifthly: Heat is emitted in all directions from the surface of an ignited body: so is light from the surface of a burning body.
Sixthly: The laws of reflection are the same in light and heat.
Other coincidences might be established, and other celebrated names added.
If this identity should be established finally, it would not effect the doctrine of the foregoing pages in the least. It would only be necessary to say, the luminiferous fluid of this essay is the well established substance now called caloric.
Addenda on Light.
1. It is now generally admitted that the real body of the sun is surrounded with a peculiar set of clouds, phosphorescent in their nature. It is also allowed that these clouds do not emit heat. And as it is well known that no one of the planets has such clouds, but receive their light from the sun, it is extremely probable that these phosphorescent clouds are intended by the Creator, to be the great dispenser of light to the solar system, by operating as the exciting cause to put the luminiferous ether in motion throughout the solar system.
By a parity of reasoning, each centre of a system may be invested with similar clouds, which operate in the same way in reference to the planets which belong to it.
2. If light were a real substance, as commonly understood, solar light must proceed from the sun by impulsion, and artificial light from burning bodies by evolution. Take the case of burning bodies. A single candle placed two miles above the surface of the earth in the air, and lighted up in that position, will instantly illuminate a space of two miles in every direction from itself, or a spherical space four miles in diameter. In this case a sufficient quantity of light is instantly evolved to fill this space, and the evolution continues as long as the candle burns. The question upon this fact is this: Can it be supposed that there is a sufficient quantity of light, in combination with a single candle, or the oxygen necessary to keep up its combustion, to fill a spherical space four miles in diameter for several hours together? This would indeed be almost incredible in view of the space filled by light evolved from a single candle.
But this difficulty would be satisfactorily solved upon the supposition that light is the effect, produced by a luminiferous ether, universally diffused, and put in motion, by which it becomes visible, by the sun, burning bodies, &c. Because, the motion which renders the luminiferous ether visible, commences instantly upon the commencement of combustion, and is propagated from the point of combustion in right lines, under the appearance of rays of light: but the motion ceases instantly on the cessation of combustion, and of course darkness instantly ensues.]
After having attended to the production of light, and noticed some of its properties, it is a paramount duty to contemplate its glorious Author; especially as by this mysterious production he himself has chosen to be represented. If creatures be excellent, what must be the Creator? and to admire the former without adoring the latter, would be profane and atheistical. “The Deity,” says Sir Isaac Newton, “in infinite space, as in his own sensorium, has an intimate perception of all things:” so we, possessing intellect, should “look through nature up to nature’s God.” Then matter, however rarefied or diversified, would serve as his minister to introduce us into his presence. A pious ancient, on being asked by a profane philosopher, How he could contemplate high things, since he had no books? answered, That he had the whole world for his book, ready open at all times, and in all places, and that he could therein read things heavenly and divine. As the visible creation is the outward expression of the existence of God, and displays several of his infinite perfections; so we should study him in the works of nature, and trace him in the operation of his hands.
The late excellent and pious Bishop Horne very beautifully observes,—“When the angels beheld the dark and disordered state of created nature upon its first production, they were, doubtless, thrown into some perplexity to conceive how it should ever be made a means of manifesting forth the glory of the Creator. But when they saw the light spring up, at the Divine command, from that blackness of darkness, and fix its residence in its tabernacle the sun, illuminating and adorning the firmament of heaven with its glorious show, and the earth with its beautiful furniture, all formed out of rudeness and confusion, then they confessed that the difficulty of the work served only to display the skill of the workmaster, which is proportionally estimated by the unpromising nature of the materials.
In like manner, whoever views the chaos to which the infinite wisdom of a presiding Providence sometimes permits the moral world to be reduced by the prevailing power of the prince of darkness, and the agency of his instruments, will scarce be able, at first, to discern any traces of the Divine counsels in a mirror so sullied and clouded over by the enormities of sinful men. Yet let him wait with patience for a little season, and those clouds shall pass away; a light shall shine, and some great end present itself to sight, so worthy of God, so beneficial to man, that standing amazed at a power able to bring the greatest good out of the greatest evil, he will be forced to cry out concerning the economy of the spiritual system, as David did concerning the operations of the natural—‘Oh Lord, how manifold are thy works! In wisdom hast thou made them all.’”[46]
Section IV.—Day and Night.
Original terms of Day and Night — Motion the effect of a Divine power — Commencement of Time — Utility of Day and Night — Religious improvement of Time — Sin moral darkness — The Gospel a Light to dispel it — A Christian the subject of a transition from the one state to the other.
The separation of light from the darkness, was the work of the first day. This was an arrangement made by infinite Wisdom, as well as a display of almighty power. When this took place, it is highly probable that God gave to the earth its rotation upon its own axis, to produce the necessary succession of day and night. “The word ערב éreb, which we translate evening, comes from the root ערב ârab, to mingle, and properly signifies that state in which neither absolute darkness, nor full light, prevails. It has nearly the same grammatical signification with our twilight, the time that elapses from the setting of the sun till he is eighteen degrees below the horizon, and eighteen degrees before he arises. Thus we have the morning and evening twilight, or mixture of light and darkness, in which neither prevails; because, while the sun is within eighteen degrees of the horizon, either after his setting, or before his rising, the atmosphere has power to refract the rays of light, and send them back to the earth. The Hebrews extended the meaning of this term to the whole duration of night, because it was ever a mingled state; the moon, the planets, or the stars, tempering the darkness with some rays of light. From the ereb of Moses came the Ερεβος Erebus of Hesiod, Aristophanes, and other heathens, which they deified, and made with nox, or night, the parent of all things. The word בקר boquer, which we translate morning, from בקר boquar, he looked out, is a beautiful figure, which represents the morning as looking out at the east, and illuminating the whole of the upper hemisphere.”[47]