Or Carbone. This substance has not yet been procured in a separate state; the idea of it is an abstract, not a sensible one: yet it is not, like phlogiston, an imaginary principle, for though on the whole the evidence of its existence is not more strong, it does not by its presence involve any contradictory quality.

The essence of carbon has been thought to consist in its absorbing light, and appearing of a black colour; but the purest form in which it is offered to our observation is that of the sparkling diamond. In the carbonic acid gas it is combined only with oxygen, for Lavoisier found that this gas contained 28 parts of carbon, and 72 of oxygen. Charcoal itself, is supposed to be carbon, with a smaller proportion of oxygen; and diamond approaches still nearer to the carbon: so that charcoal has been called an oxide of diamond.

Carbon unites with many bodies, which are denominated carbonates and carburets. It does not, however, combine in the form of charcoal with oxygen gas, till its temperature be raised to 370° of Fahrenheit, its point of ignition. It then burns in this gas with a brilliant flame, and the carbonic acid gas is the result. This gas also escapes in respiration, and in many other animal processes. In the form of carbonic acid, it exists copiously in the earth, united with limestone, and is found in many other bodies. It occurs alone in caverns, and particularly in the grotto del Cani in Sicily.

It particularly engages our attention in this work, as it is the distinguishing ingredient in vegetable bodies, while the azote equally discriminates animal substances. It is derived from the earth, for of whatever kind manures are, they all contain carbon, or greedily extract it from the air. From thence it is introduced into the animal system; and, combining with oxygen, is discharged in respiration in the form of carbonic acid gas. We have already noticed this change, particularly under the article of Calidum innatum, and shall return to it under that of Respiration. In the system it produces no particular effect. In the stomach, as we have seen under the head of Aquae minerales, it acts as a stimulant, and relieves vomiting.