explodes immediately above the balloon, the envelope will be torn
to shreds and a violent explosion of the gas will be precipitated.
But as a matter of fact, it is extremely difficult to place a
shrapnel shell so as to consummate this end. The range is not
picked up easily, while the timing of the fuse to bring about the
explosion of the shell at the critical moment is invariably a
complex problem.

One favourite method of finding the range of a balloon is shown
in the accompanying diagrams. The artillery battery is at B
and the captive balloon, C, is anchored at A. On either
side of B and at a specified distance, observers O1 and O2
respectively are stationed. First a shell is fired at "long"
range, possibly the maximum range of the gun. It bursts at D.
As it has burst immediately in the line of sight of B, but with
the smoke obscured by the figure of the balloon C, it is obvious
to B that the explosion has occurred behind the objective, but at
what distance he cannot tell. To O1 and O2,however, it is seen
to have burst at a considerable distance behind C though to the
former it appears to have burst to the left and to the second
observer to the right of the target.

Another shell, at "short" range, is now fired, and it bursts at
E. The explosion takes place in the line of sight of B, who
knows that he has fired short of the balloon because the latter
is eclipsed by the smoke. But the two observers see that it is
very short, and here again the explosion appears to O1 to have
occurred to the right of the target, while to O2 it has evidently
burst to the left of the aerostat, as revealed by the relation of
the position of the balloon to the bursting of the shell shown in