difficult and eventually becomes
extremely dangerous.

A wind, if of appreciable strength, develops another and graver danger.
Greater strain will be imposed upon the cable, while if the wind be
gusty, there is the risk that the vessel will be torn away from
its anchoring rope and possibly lost. Thus it will be seen that the
effective utilisation of a captive balloon is completely governed by
meteorological conditions, and often it is impossible to use it
in weather which exercises but little influence upon dirigibles or
aeroplanes.

The captive balloon equipment comprises the balloon, together with the
observer's basket, the wire-cable whereby it is anchored and controlled,
and the winding apparatus. Formerly a steam engine was necessary for
the paying in and out of the cable, but nowadays this is accomplished by
means of a petrol-driven motor, an oil-engine, or even by the engine of
an automobile. The length of cable varies according to the capacity of
the balloon and the maximum operating height.

The average British balloon is able to lift about 290 or 300 pounds,
which may be taken to represent the weight of two observers. On the
other hand, the French and German balloons are able to carry four times
this weight, with the exception of the French auxiliaries, which are
designed to lift one observer only. The balloons of the two latter
Powers have also a greater maximum altitude; it is possible to ascend to
a height of some 2,000 feet in one of these.

The observing station is connected with the winding crew below either
by a telephone, or some other signalling system, the method practised
varying according to circumstances. In turn the winding station is
connected with the officer in charge of the artillery, the fire of which
the captive balloon is directing. The balloon observer is generally
equipped with various instruments, such as telescope, photographic
cameras, and so forth, so as to be able, if necessary, to prepare a
topographical survey of the country below. By this means the absence
of reliable maps may be remedied, or if not regarded, as sufficiently
correct they may be checked and counter-checked by the data gained
aloft.

Seeing that the gas has to be transported in cylinders, which are
weighty, it is incumbent that the waste of this commodity should be
reduced to the minimum. The balloon cannot be deflated at night and
re-inflated in the morning--it must be maintained in the inflated
condition