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.