Our author does not say in what this virulence consists. In the cases of those who die with the _tokens_ upon them, the cause is plainly within the body; the destroying power acting with greatest efficacy below the skin in the soft substance of the flesh. Where the patient is suddenly seized in the manner described by Dr. Guthrie, the cause seems to be something foreign to the body suddenly inhaled, the effects being similar to those of fixed air when drawn in by the breath, and of consequence easily expelled by a vigorous action of the powers of the system. Guthrie observes, that, in such cases, it seems “as if the contagious matter existed in a very loose state in the first passages at the beginning of the disease.” In the production of those _tokens_ mentioned by Dr. Hodges, we know that there must have existed in the body a certain cause capable of totally destroying the parts, and reducing them to an hard eschar, similar to that produced by fire or by a caustic. As we are unacquainted with any thing capable of producing this effect but fire, we can attribute the origin of these tokens to nothing else but the emission of the latent heat of both the solids and fluids which compose these parts, and their consequent transmutation into an hard, and as it were charred, substance. That such an emission of latent heat does in some cases take place is evident from the production of a great quantity of sensible heat when certain substances are mixed together. Thus, upon mixing together oil of vitriol, oil of turpentine and strong spirit of nitre, the whole mixture will take fire and burn violently, though two of the ingredients, viz. oil of vitriol and spirit of nitre, are by themselves incapable of being inflamed. In like manner if strong spirit of nitre be poured upon oil of cloves or sassafras, the mixture will burst out into a violent flame. Water poured upon quick lime occasions great heat, and seems in great part to be converted into a solid substance; for only a small part evaporates, and the slaked lime falls into a powder to appearance perfectly dry, and from which the moisture cannot be expelled without a very violent fire. In this case Dr. Black is of opinion that the heat comes from the water, which, as we have already seen, contains a great quantity of it in a latent state. But, according to his experiments, the emission of 135 degrees of heat is sufficient to reduce water to a state of solidity; and the heat of lime when slaking is so much superior to this, that ships have frequently been set on fire by it. We must therefore either say that water in certain circumstances can part with much more than 135 degrees, or that the lime itself emits part of the heat it contains. This last indeed seems to be the more probable supposition of the two; for though fluids contain more heat in proportion to their bulk than solid bodies, we have no reason to suppose that the latter contain none