ss, 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
is a most unreliable and unsociable element. Like Kipling's cat it walks
by its wild lone.

It is not so bad as Argon the Lazy and the other celibate gases of that
family, where each individual atom goes off by itself and absolutely
refuses to unite even temporarily with any other atom. The nitrogen
atoms will pair off with each other and stick together, but they are
reluctant to associate with other elements and when they do the
combination is likely to break up any moment. You all know people like
that, good enough when by themselves but sure to break up any club,
church or society they get into. Now, the value of nitrogen in warfare
is due to the fact that all the atoms desert in a body on the field of
battle. Millions of them may be lying packed in a gun cartridge, as
quiet as you please, but let a little disturbance start in the
neighborhood--say a grain of mercury fulminate flares up--and all the
nitrogen atoms get to trembling so violently that they cannot be
restrained. The shock spreads rapidly through the whole mass. The
hydrogen and carbon atoms catch up the oxygen and in an instant they are
off on a stampede, crowding in every direction to find an exit, and
getting more heated up all the time. The only movable side is the cannon
ball in front, so they all pound against that and give it such a shove
that it goes ten miles before it stops. The external bombardment by the
cannon ball is, therefore, preceded by an internal bombardment on the
cannon ball by the molecules of the hot gases, whose speed is about as
great as the speed of the projectile that they propel.

[Illustration: (C) Underwood & Underwood

THE HAND GRENADES WHICH THESE WOMEN ARE BORING will contain potential
chemical energy capable of causing a vast amount of destruction when
released. During the war the American Government placed orders for
68,000,000 such grenades as are here shown.]

[Illustration: (C) Internationa