With respect to _caloric_, it may not be improper to offer some remarks.[1] The hypothetical element of phlogiston having given way to the antiphlogistic theory at present received, our ideas respecting caloric are predicated on facts. Caloric is a term, which expresses heat, or matter of heat. In pyrotechny, we have merely to consider it in a free, or uncombined state; but as the subject is interesting, we purpose to notice it very briefly under the following heads: viz. its nature; the manner it is set in motion; its tendency to a state of rest; the changes it produces on bodies; and the instruments for measuring its intensity. As to the nature of caloric, different opinions are entertained. We know the effect of heat: if we touch a substance of a higher temperature than our bodies, we call it hot, and _vice versa_. The one is evidently the accession, and the other the abstraction, of caloric. The latter is merely relative as respects ourselves; for the effect depends on our feelings, and the sensation of hot or cold is therefore governed by them.[2] Caloric, however, is considered to be a substance, composed of inconceivably small particles; but count Rumford and sir H. Davy are of a contrary opinion, namely, that it depends upon a peculiar motion and not on a subtle fluid. As the effect of caloric, according to their view, depends on motion, the agencies by which this is effected are of the first importance. That it exists in all bodies in a state of rest, and in a greater or smaller quantity, and consequently in a relative proportion, is well known, and on this, the capacities of bodies for caloric is founded. The capacities of bodies for heat are changed by various means, and caloric is put in motion; and, according to its quantity, the bodies may be either cold or hot. When the surrounding bodies become heated, they receive this caloric thus set free, and, in this view, the absolute quantity of their heat is increased. This state of rest, to which caloric is subject, may be destroyed either by an increase or a diminution of the capacity of a body. If caloric be put in motion by causes of any kind, which influence the capacities of different bodies, a theory maintained by Davy, then as the capacity for heat is changed so is free heat produced. Diminish the capacity of a body, its excess will of course be given out, and distribute itself among the surrounding bodies, which become heated; but increase the capacity, and a different effect ensues. The body absorbs caloric, by which its capacity is increased, and cold is produced. Caloric, whether considered a substance, or an attribute, possesses, nevertheless, this property, that when it is given out, as in the mixture of sulphuric acid and water, which occupies a less space than both in a separate state, the sensation of heat follows; and when it is absorbed, as in the various freezing mixtures, or in a mixture of snow and common salt, the sensation of cold is excited. The causes,