only thing you can do is to hide and shoot back. Now you cannot hide if
you send up a column of smoke by day and a pillar of fire by night--the
most conspicuous of signals--every time you shoot. So the next step was
the invention of a smokeless powder. In this the oxygen necessary for
the combustion is already in such close combination with its fuel, the
carbon and hydrogen, that no black particles of carbon can get away
unburnt. In the old-fashioned gunpowder the oxygen necessary for the
combustion of the carbon and sulfur was in a separate package, in the
molecule of potassium nitrate, and however finely the mixture was
ground, some of the atoms, in the excitement of the explosion, failed to
find their proper partners at the moment of dispersal. The new gunpowder
besides being smokeless is ashless. There is no black sticky mass of
potassium salts left to foul the gun barrel.

The gunpowder period of warfare was actively initiated at the battle of
Cressy, in which, as a contemporary historian says, "The English guns
made noise like thunder and caused much loss in men and horses."
Smokeless powder as invented by Paul Vieille was adopted by the French
Government in 1887. This, then, might be called the beginning of the
guncotton or nitrocellulose period--or, perhaps in deference to the
caveman's club, the second cellulose period of human warfare. Better,
doubtless, to call it the "high explosive period," for various other
nitro-compounds besides guncotton are being used.

The important thing to note is that all the explosives from gunpowder
down contain nitrogen as the essential element. It is customary to call
nitrogen "an inert element" because it was hard to get it into
combination with other elements. It might, on the other hand, be looked
upon as an active element because it acts so energetically in getting
out of its compounds. We can dodge the question by saying that nitrogen