Q. Whence does the heat of our own body arise?
A. The carbon of the blood combines with the oxygen of the air inhaled, and produces carbonic acid gas; which produces heat in a way similar to burning fuel.
Q. Whence does the heat of a dunghill arise?
A. The straw, &c. of the dunghill undergoes fermentation as it decays: the fermentation produces carbonic acid gas, and heat is evolved by a species of combustion (as in the two former cases).
Q. What changes do vegetables undergo from putrefaction?
A. The hydrogen of the vegetables combines with the oxygen of the air, and forms water: again, the carbon of the vegetables combines with oxygen of the air, and forms carbonic acid gas. Putrefaction, therefore, is only another species of combustion.
Q. What changes do animal bodies undergo from putrefaction?
A. The same as vegetables, with this addition—they give out ammonia, sulphur, and phosphorus also; which causes the offensive smell of putrefying animal bodies.
Q. Why is lime heated by a kiln?
A. All marl and chalk abound in carbonic acid; and (when heated by a fire) the carbonic acid flies off in gas, producing great heat.