Fluids, from their very nature and constitution, contain a greater quantity of caloric in a latent state than solid bodies: indeed it is now universally admitted, and may be easily proved, that the fluidity of all bodies is altogether owing to the quantity of fire which they retain in this latent or combined state, the elasticity of which keeps their particles remote from each other, and prevents their fixing into a solid mass. All bodies, therefore, in passing from a fluid to a solid state, emit a quantity of fire or heat. When water is thrown upon quick lime, it is absorbed by the lime, and in this state it is capable of retaining a much smaller quantity of caloric than in its natural state; on the slacking of lime, therefore, a very intense heat is produced, the matter of fire which preserved the water fluid being disengaged and detached. If spirit of vitriol is added to strong oil of turpentine, they will condense into a solid mass, and a great quantity of heat will be sensibly emitted. Upon the same principle it will be found, on the other hand, that when any body passes from a solid to a fluid state, the adjacent bodies will be deprived of a quantity of their natural heat.
[This theory of what is called burning lime, is not sufficiently clear. Fire does not enter into the pores of the lime by burning. The mineral commonly used for procuring quick lime is the carbonate of lime, or common limestone, which is composed of carbonic acid with a small quantity of water, 43, and lime 57, in 100 parts. By submiting it to a strong heat, the carbonic acid is driven off, and the quick or pure lime remains, which is an oxide of calcium. The loss in weight is owing to the expulsion of the carbonic acid, with the small portion of water. By adding water to the quick lime, it is dissolved, and falls into a powder. This process is called slacking lime, and the product, slack-lime. During the process a large quantity of heat is disengaged; and if the slacking be done in the dark, light is also observed to be thrown out. This heat is given out by the water, not the lime. The lime having a greater affinity for the hydrogen of the water than exists between the hydrogen and oxygen in water, seizes upon it, and the oxygen passes off, together with the latent caloric of the water, and thus the heat is produced which is observed in slacking lime. The hydrogen of the water combines with the lime and becomes solid, forming an hydrate of lime, which is the common slacked lime used in mortar.]
The matter of fire is elastic, as is proved evidently from all its effects. There is indeed reason to believe, that caloric is the only fluid in nature which is permanently elastic, and that it is the cause of the elasticity of all fluids which are esteemed so. From the elasticity of this element it results, that all natural bodies can only retain a certain quantity of it, without undergoing an alteration in their state and form. Thus a moderate quantity of fire admitted into a solid body expands it; a still larger quantity renders it fluid; and if the quantity is still increased, it will be converted into vapor.
Caloric expands all bodies which it penetrates, more or less, in proportion to its quantity, and to the nature of those bodies. The expansion of water, even previous to its assuming the form of vapor, may be seen in an easy experiment. If a quantity of cold water, contained in a clear flask, is immersed in a vessel of boiling water; as the heat enters, the water in the flask will be seen to rise in the neck till it overflows.
An iron rod a foot long being heated red hot, became 1-60 longer than before; and a glass cylinder, a fathom long, under the same circumstances, gained 1-50 in length. A metalline ring thus heated was increased 9-100 in its diameter; and a glass globe became extended 1-100 part by the heat of the hand only applied to its surface.[33]
The general effects of caloric are to increase the bulk of the substances with which it unites, and to render them specifically lighter than they were before; but in whatever quantity it is accumulated in bodies, it never adds to their absolute weight. Caloric favors the solution of salts, and promotes the union of many substances. In other cases it serves to separate bodies already united; so that in the hands of chemists it is the most useful and powerful agent with which they are acquainted. It is the cause of fluidity in all substances which are capable of becoming fluid, from the heaviest metal to the lightest gas. Let it be remembered that all fluids are formed from solids by an addition of caloric; and that, by abstracting this caloric, solids would be reproduced. It insinuates itself among their particles, and invariably separates them in some measure from each other. We have reason to believe that every solid substance on the face of the earth might be converted to a fluid, or even a gas, were it submitted to the action of a very high temperature in peculiar circumstances.[34]
[The general and aggregate bearing of the facts and experiments which are now known, render the statement here made by Mr. Wood extremely probable, viz; That caloric is a very subtle fluid which pervades in large quantities every particle of matter in the universe—that it is the agent which regulates the densities of all bodies, and by consequence, regulates in some measure their weight and dimensions. It is considered as an almost settled question, that a stratum of caloric surrounds each ultimate particle of every body, so that the ultimate particles of bodies do not, and cannot be made to touch each other. Their inherent inclination to come into actual contact is called their attraction of cohesion: the power of this attraction is in proportion to the distance at which they are kept from each other by the atmosphere of caloric which intervenes between them. This atmosphere of caloric is idio-repulsive: of course the particles of caloric have an inherent repulsion among themselves, and are ever struggling to get further asunder.
This idio-repulsive nature of caloric is the great, and constant antagonist power to the attraction of cohesion. Caloric has a tendency to drive the particles of matter further from each other, and these particles have a mutual tendency to approach. Hence these two principles are ever in conflict. As a general rule we may say, when the attraction of cohesion prevails greatly, the body becomes solid: when the two forces are pretty nearly balanced, the body becomes liquid: when the caloric prevails greatly, the body becomes gaseous.
There is sufficient reason to believe, that every body in nature might be raised to a gaseous state by the addition or action of a sufficient quantity of caloric: and there is, probably, a sufficient quantity in nature, to render the whole universe gaseous, were it sufficiently excited to a state of freedom. It is a well known fact, that all the metals are fusible by heat, and many of them have been volatalized, and it is extremely probable all of them may be.
As caloric regulates the density of bodies, by resisting and modifying the influence of the attraction of cohesion: if it were entirely withdrawn from nature, or the whole of it rendered perfectly latent, all matter would become perfectly solid and fixed: even water and air would assume the solidity of the diamond.
We must, therefore, regard caloric as the great conservative principle of the Universe, and yet capable, if called into action, of destroying it instantly.
These views strongly corroborate our paper on chaos.]
From the experiments of General Roy, in the 75th volume of the Philosophical Transactions, it appears that the expansion of a steel pendulum of a clock is such, that every four degrees of the thermometer will cause a variation of a second per day; and that the difference between the going of a clock in summer and winter will be about six seconds per day, or one minute in ten days, owing to the metallic pendulum varying in length with every change of temperature. A knowledge of this circumstance gave rise to Harrison’s self-regulating time-piece, which, by the different expansion of different metals, accommodates its movements to every change of seasons or climate.
The fire deposited below the surface of the earth is peculiarly important, having produced earthquakes and volcanic eruptions. Dr. Watson, late Bishop of Llandaff, in his Chemical Essays, says, The most remarkable changes which have taken place in the form and constitution of the earth, since the deluge, have probably been produced by subterraneous fires; for it is to their agency that philosophers ascribe volcanos and earthquakes; those tremendous instruments of nature, by which she converts plains into mountains, the ocean into islands, and dry land into stagnant pools. Mr. Lemery, as far as I have been able to learn, adds the learned Bishop, was the first person who illustrated, by actual experiment, the origin of subterraneous fires. He mixed twenty-five pounds of powdered sulphur with an equal weight of iron filings; and having kneaded the mixture together, by means of a little water, into the consistency of a paste, he put it into an iron pot, covered it with a cloth, and buried the whole a foot under ground. In about eight or nine hours time the earth swelled, grew warm, and cracked: hot sulphureous vapors were perceived: a flame which dilated the cracks was observed; the superincumbent earth was covered with a yellow and black powder: in short, a subterraneous fire, producing a volcano in miniature, was spontaneously lighted up from the reciprocal actions of sulphur, iron, and water.
Volcanic eruptions are awfully terrific, and sometimes extensively destructive. The violent eruption of Vesuvius, in 1767, is reckoned the 27th since that which destroyed the cities of Herculaneum and Pompeii, in the reign of the Emperor Titus; and this eruption of 1767, has been succeeded by several others. Of the eruptions of Ætna, Mr. Oldenburg has given a historical account in the Philosophical Transactions, No. xlviii. p. 967. A very great eruption of this mountain was in the year 1669. The progress of the lava, or fiery deluge, was at the rate of a furlong a day. It advanced into the sea 600 yards, and was then a mile in breadth. It had destroyed, in forty days, the habitations of 27,000 persons; and of 20,000 inhabitants of the city of Catanea, only 3,000 escaped. This inundation of liquid fire, in its progress, met with a lake four miles in compass, and not only filled it up, although it was four fathoms deep, but raised it into a mountain. Borelli, an ingenious Neapolitan, has calculated, that the matter discharged at this eruption was sufficient to fill a space of 93,838,750 cubic spaces. The lava which ran from it is fourteen miles in length, and, in many parts, six in breadth. There have been no such eruptions since, although there have been signs of many, more terrible, that preceded it.[35]