I shall now give a few out of many specimens of coal, to show its composition, and so look at it in a practical point of view. For ordinary purposes, there is no doubt the “best” is the best; but whether that best is Welsh, or Newcastle, or Scottish, I do not pretend to say; for the various kinds of coal are suited for different purposes, and what may be refuse in one direction may be of the greatest use in another.
In experiments undertaken with a view to determine what coals were best suited for our steam-navy, Sir Henry de la Beche and his associates tried nearly all the kinds known in Britain, and compared them too with those artificial fuels which are made up from coal-refuse, and are extremely valuable in their way.
I can only give a few examples, and shall refer my young readers—they are older now than when the lecture began, and will not mind a little dry study—to the book itself, if they require more information.
They tried these coals to see how much they held of carbon, which supplies the heat; of hydrogen, which gives the flame; of oxygen, which is worse than useless in the coal, though essential in the air that is to support the combustion; and, lastly, the quantity of ashes left after the coal was consumed.