Q. Why are timbers, which are to be exposed to damp, charred?
A. Charcoal undergoes no change by exposure to air and water; therefore timber will resist weather much longer, after it has been charred.
CHAPTER V.
LAMPS AND CANDLES.
Q. Of what are oil, tallow, and wax composed?
A. Principally of carbon and hydrogen gas. The solid part is carbon, the volatile part is gas.
Q. What is carbon?
A. A solid substance, generally of a black colour; well known under the forms of charcoal, lamp-black, coke, black-lead, &c.
Q. What is hydrogen gas?