Fire is not hot, although it burns the flesh and promotes pain. Matter, which is unalterable, cannot be made hot or cold, neither is there anything to make it so. If a limb be made rigid, or the nerves of sensation be removed, or the function of the nervous fluid be obstructed, the limb may be burned off unconsciously. Heat is a sensation effected through excitement of the brain; out of the brain there is neither excitement nor heat. The fire does not excite the brain, but the nervous fluid; and although the sensation is not hot, it is imagined that the cause must be hot, which is false reasoning. The chymist finds heat creviced in all things, even those which he admits are destroyed by heat—gunpowder and ice. How can flame be hot, when just obtained from the gases of decomposed ice water? or, if hot, sui generis, it must have been hot frozen flame in the original ice.

Modern philosophy adopts different kinds of heat,—animal, culinary, and latent heat. The first is our own feeling excited by means of fire in the sensitive centre, the brain; also by exercise and disease, in the absence of fire. How is the spark from the flint or from the steel to saturate a bushel of coal with heat? How, again, does "heat come to an equilibrium in all surrounding bodies," when some portion of the coal may be black cold, and others red hot—using the popular terms—in the fire-place, at the same time, and while the air in the chamber is indexing zero? Latent heat is of the philosopher's own peculiar making; and on the "great discovery" the most unbounded praise is still bestowed. Latent heat, "which all bodies possess without being heated," which, "heats nothing," and is not hot, is cold heat, and should be nomenclatured such, or, absurd heat. Are not Instructors less than half-reasoners and unnatural philosophers, who abide by and teach such consummate nonsense: on a par with which is the discovery of "latent dark light"—"of black being formed by the intermixture of two luminous rays at the point of intersection in the spectrum," which is the same as feelable darkness; after which, there only remains for "new discovery," latent sound, for inking on, thence vibrating from, a sheet of music-paper; and latent motion, to keep a stone at rest, the quantity of motion in the world having been already ascertained arithmetically to a fraction; the last-day discovery, the quantity of right reason, is the small remaining trifle to be discovered. Radiation of heat and cold by fire and ice, being inconsistent with the inertia of matter, is an erroneous and greatly-misleading assumption, although proved through the nicest experiments, according to the experimenter's ideas.

Instead of fire communicating anything to bodies, fire promotes loss to everything in its neighbourhood. The bars of stoves, iron pokers, steam-boilers; all culinary vessels; coal, wood, candles, paper, linen, all suffer loss by means of fire; cinders, charcoal, tinder, are but remains: to which it is no exception that some bodies acquire substance and weight in becoming oxydes; because, previous to acquiring oxygen from the air, they must have lost elementary matter to the fire to make spaces for the oxygen to enter, otherwise the open air should oxydize equally, in the absence of fire.

The loss, or matter of loss which fire promotes to fluids, appears as air-beads on the sides and bottom within the vessel on the fire, before the water comes to ebullition: these beads cannot be made to rise in the water by any manner of agitation, which is proof they have not come from the fire, and through the rigid bottom, or ascent and escape are inevitable. When the bottom has been sufficiently de-electrised by the fire, they are pressed through it to the fire; or if the vessel be removed and placed on the ground, they become dispersed through the water insensibly. The like spherules collect on an egg while boiling, which cannot be anything issued from the fire to the surface of the water, then precipitated on the egg. On the bottom of a glass-retort suspended over a lamp, the like spherules collect, from which it is supposed that water never touches the bottom of any containing vessel; it must touch that which it wets.

That air suffers loss to fire, is made evident by the air being deprived of, or losing its oxygen during combustion; and from both fire and flame becoming extinguished in a limited quantity of respirable air, in consequence of having lost its oxygen to the combustible, while in the state of fire.

Solids, as polished metals and glass, when they experience no change of weight, lose to the fire imponderable elementary matter only. So is it when the hand is presented to the fire, it loses electric matter, and the loss it suffers promotes the sensation of heat: when the hand afterwards touches a body, supposed to be cold, it acquires elementary matter from that which is touched. In every instance the body, solid or fluid, supposed to be heating, is losing elementary matter; and that which is said to be cooling, is acquiring the like matter; the hand loses to the former and receives from the latter electric matter.