e 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 Fig. 3.

A third round is fired, and the shell explodes at F. In this instance
the explosion takes place below the balloon. Both the observers and the
artillery man concur in their deductions upon the point at which
the shell burst. But the shell must explode above the balloon, and
accordingly a fourth round is discharged and the shell bursts at G.

This appears to be above the balloon, inasmuch as the lines of sight
of the two observers and B converge at this point. But whether the
explosion occurs immediately above the vessel as is desired, it is
impossible to say definitely, because it may explode too far behind to
be effective. Consequently, if this shell should prove abortive, the
practice is to decrease the range gradually with each succeeding round
until the explosion occurs at the critical point, when, of course, the
balloon is destroyed. An interesting idea of the difficulty of picking
up the range of a captive balloon may be gathered from the fact that
some ten minutes are required to complete the operation.

But success is due more to luck than judgment. In the foregoing
explanation it is premised that the aerial vessel remains stationary,
which is an extremely unlikely contingency. While those upon the ground
are striving to pick up the range, the observer is equally active in his
efforts to baffle his opponents. The observer follows each successive,
round with keen interest, and when the shells appear to be bursting at
uncomfortably close quarters naturally he intimates to his colleagues
below that he desires his position to be changed, either by ascending to
a higher point or descending. In fact, he may be content to come to the
ground. Nor must the fact be overlooked that while the enemy is trying
to place the observer hors de combat, he is revealing the position of
his artillery, and the observer is equally industrious in picking up the
range of the hostile guns for the benefit of his friends below.

When the captive balloon is aloft in a wind the chances of the enemy
picking up the range thereof are extremely slender, as it is continually
swinging to and fro. While there is always the possibility of a shell
bursting at such a lucky moment as to demolish the aerial target, it is
generally conceded to be impossible to ind