ought me into contact with the heavy manufacturers throughout
the Eastern States, and during that long experience I was particularly
impressed with a peculiarity common to the mill owners, which, I
believe it may be said with truth, is equally common to those
interested in locomotive engineering, namely, how much we overlook
common, every-day facts. For instance, we burn coal; that is, we think
we do, and boilers are put into mills and upon railroads, and we
suppose we are burning coal under them, when in reality we are only
partially doing so. We think that because coal is consumed it
necessarily is burned, but such is frequently very far from the fact.

I wish upon the present occasion to make merely a sort of general
statement of what I conceive to be combustion, and what I conceive to
be a boiler, and then to try to make a useful application of these
ideas to the locomotive.

Treating first the subject of combustion, let us take the top of the
grate-bars as our starting point. When we shovel coal upon the grate
bars and ignite it, what happens first? We separate the two
constituents of coal, the carbon from the hydrogen. We make a gas
works. Carbon by itself will burn no more than a stone; neither will
hydrogen. It requires a given number of equivalents of oxygen to mix
with so many equivalents of carbon, and a given number of equivalents
of oxygen to mix with so many of hydrogen to form that union which is
necessary to produce heat. This requires time, space, and air, and one
thing more, viz., heat.

I presume that most of you have read Charles Williams' treatise upon
"Combustion," which was published many years ago, and which until
recently was often quoted as an absolute authority upon the art of
burning fuel under boilers. Mr. Williams in his treatise accurately
describes the chemistry of combustion, but he has misled the world for
fifty years by an error in reasoning and the failure to discuss a
certain mechanical fact connected with the combination of gases in the
process of combustion. He said: "What is the use of heating the air
put into a furnace? If you take a cubic foot of air, it contains just
so many atoms of oxygen, neither more nor less. If the air be heated,
you cause it to assume double its volume, but you have not added a
single atom of oxygen, and you will require twice the space for its
passage between the grate bars, and twice the space in the furnace,
which is a nuisance; but if the air coul