philosophers of ancient Greece. Here is the foundation of all physical logic, and a key to the whole mechanism of nature. For as it is certain that all the changes and transformations of matter are the immediate effects of motion, it follows that a complete knowledge of the prime mover would lead to a perfect theory of physics.

Since the time of Sir Isaac Newton, attraction and repulsion have been generally regarded as ultimate principles of action, for which no reason can be assigned.* But if it be a fact, that the elastic force of bodies is augmented by every addition, and diminished by every abstraction of caloric, it is obvious that the entire privation of

* After referring to his theory of planetary motion, Newton observes in his Preface to the Principia,-"many things induce me to suspect, that all the rest of the phenomena of nature may depend upon certain forces, by which the particles of bodies, by some causes hitherto unknown, are mutually impelled towards each other in regular figures, or are repelled and recede from one another; which forces being unknown, philosophers have hitherto attempted the investigation of nature in vain." Sir H. Davy also observes, that "the various forms of matter, and the changes of these forms, depend upon active powers, such as gravitation, cohesion, calorific repulsion or heat, chemical attraction, and electrical attraction." (Chemical Philosophy, p. 67.) Dr. Arnott further states, that "attraction and repulsion are ultimate facts, which admit of no explanation in the present state of science." (Elements of Physics.) And Sir John Herschel adds, that "we have no means of further analyzing the phenomena of cohesion and elasticity, but must regard them, until we see reasons to the contrary, as ultimate phenomena, referable to the direct agency of an attractive and repulsive force." (Introduction to the Study of Nat. Philosophy, s. 80.)

it, would destroy the repulsive power of their particles. And as we have seen, that without caloric, they could have no power of motion, it is evident that they could neither approximate nor recede from one another; consequently, that both attraction and repulsion one and the same agent. proved that this agent is the pores of bodies, as in the stellary spaces—and cannot be traced to any more comprehensive principle—it must be allowed to possess all the attributes of a primary efficient cause. For, nothing can merit the title of a vera causa, unless it be something which has the power of moving itself, and of generating motion in other bodies.

are modified effects of Moreover, if it can be every where present—in

It is equally evident, that whatever the cause of attraction and repulsion may be, it must determine all the phenomena of cohesion, chemical affinity, crystallization, elasticity,* decomposition,

* If the particles of the atmosphere and other bodies were not surrounded by caloric, there could be no vibrations, (in which heat has been supposed to consist,) therefore no sound. And here it is worthy of notice, that the velocity with which sound is propagated through different media, is directly in proportion to their elasticity, ceteris paribus. For example, it travels through the atmosphere when at the temperature of 32°, at the rate of 1090 feet per second; but when at 62o, it travels 1125 feet per second. It also moves at the rate of 3375 feet per second through hydrogen gas, which contains a much larger amount of caloric around its particles, than the same weight of atmospheric air, or any other gas, as will be shewn hereafter. In accordance with the above facts, it is well known that sound is transmitted more

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and recombination. When I come to treat of the mode in which caloric produces opposite effects, it will be found that in certain proportions it causes the particles of ponderable matter to separate, while in other proportions it forces them to unite:-that the aggregate force of attraction by which it tends to unite with the particles of gross matter, holds them together, and maintains the earth in the globular form:-in short, that all the phenomena of nature may be referred to the law by which caloric repels its own particles, and attracts those of ponderable

matter.

That the quantity of evaporation and rain throughout the earth is in proportion to the heating power of the sun, ceteris paribus, would seem to be a self-evident proposition. And it will be shewn hereafter from numerous scientific observations, that the annual average amount

distinctly, and rapidly, through light and resinous, or the more combustible species of wood, than through such as are dense, less elastic, and therefore contain less of the elastic æther termed caloric. It also moves with greater velocity through water than glass, and more swiftly through either than through rocks and metals, if we make allowance for the greater density of the latter. For it was found by MM. Biot and Colladon, that it was transmitted through water at 46°, at the rate of 4704 feet per second; and through cast iron at 61°, at the rate of 11,090 feet per second. But the specific gravity of cast iron is nearly eight times that of And we shall find that it contains a far greater amount of caloric around its particles than the same weight of iron, although less than an equal bulk of iron.

water.

of rain within the tropics, except in desert places, is about 100 inches, or three times greater than in the middle latitudes; and about nine times greater than in the polar regions. Hence the enormous size of the tropical rivers, compared with those of the higher latitudes. For example, it has been found that the Orinoco, which drains only 400,000 square miles of territory, discharges more water into the sea than the Mississippi, which drains 1,350,000 square miles.* It will also be shewn, that the quantity of lightning throughout the earth, diminishes from the torrid zone; where during the rainy season, it occurs almost every day, for nearly half the

*It has been estimated by geographers, that about thirty-three cubic miles of water are discharged daily into the sea by all the rivers of the earth. So that if this calculation be correct, or even an approximation to the truth; and if the same proportion of rain falls into the sea as on a given area of dry land, it follows that nearly 140 cubic miles of water must be carried into the atmosphere every twenty-four hours, and again precipitated in the form of rain and snow. Such are the vast forces which caloric is continually exerting in the phenomena of meteorology, without any reference to those violent commotions of the atmosphere termed hurricanes, tornadoes, and other less impetuous winds. Nor is it unworthy of passing notice; that as the quantity of water diffused through the atmosphere is in proportion to the heating power of the sun, the barometer stands higher, on an average, within the tropics than in the middle or polar latitudes; as proved by the observations of Erman, laid before the French Academy of Sciences,-after my chapter on the barometer had been printed. More water is also converted into steam during the heat of the day, and more steam is condensed into water during the coldness of night, which is the most convenient period for rain, as it does not then impede the labours of husbandry.

year,-on to the polar regions, where it scarcely ever lightens.

But were it not for the union of caloric with the particles of ponderable matter, there could be no fluidity of the ocean, which would be stationary as the solid frame-work of the mountains. Were it not for the heating power of the sun, there could be no contractions and expansions of the atmosphere, therefore no winds, nor fluctuations of the barometer. But in the present order of things, not an atom of the great aerial ocean is wholly quiescent for a single moment of time. Its tropical portions being constantly expanded by the influence of a vertical sun, rise and give place to the denser air of colder latitudes; by which a perpetual circulation is kept up, as described in the 1st chapter of Ecclesiastes, v. 6. "The wind goeth toward the south, and turneth about unto the north: it whirleth about continually, and returneth again according to its circuits.'

If the earth were of uniform surface and elevation, there would be a gradual diminution of temperature from the equator to the poles, and the winds would be as regular as the movements of the heavenly bodies. But owing to the present distribution of land and sea, mountains and valleys, plains and woods; the temperature of the globe is infinitely diversified, even in the same latitudes; by which the phenomena are rendered proportionally complex. And as the changes of