y
adapted, but which had previously more or less been ignored. The
British Army possessed indifferent maps of the Orange Free State and the
Transvaal. This lamentable deficiency was remedied in great measure by
recourse to topographical photographs taken from the captive balloons.
The guides thus obtained were found to be of extreme value.

During the early stages of the war the hydrogen was shipped in cylinders
from the homeland, but subsequently a manufacturing plant of such
capacity as to meet all requirements was established in South Africa.
The cylinders were charged at this point and dispatched to the scene of
action, so that it became unnecessary to transport the commodity from
Britain. The captive balloon revealed the impregnability of Spion Kop,
enabled Lord Roberts to ascertain the position of the Boer guns at the
Battle of Paardeburg, and proved of invaluable assistance to the forces
of General White during the siege of Ladysmith.

CHAPTER II. THE MILITARY USES of THE CAPTIVE BALLOON

Although the captive balloon is recognised as indispensable in military
operations, its uses are somewhat limited. It can be employed only in
comparatively still weather. The reason is obvious. It is essential that
the balloon should assume a vertical line in relation to its winding
plant upon the ground beneath, so that it may attain the maximum
elevation possible: in other words, the balloon should be directly
above the station below, so that if 100 yards of cable are paid out the
aerostat may be 100 yards above the ground. If a wind is blowing, the
helpless craft is certain to be caught thereby and driven forwards or
backwards, so that it assumes an angle to its station. If this become
acute the vessel will be tilted, rendering the position of the observers
somewhat precarious, and at the same time observing efficiency will be
impaired.

This point may be appreciated more easily by reference to the
accompanying diagram. A represents the ground station and B the position
of the captive balloon when sent aloft in calm weather, 300 feet of
cable being paid out. A wind arises and blows the vessel forward to the
position C. At this point the height of the craft in relation to the
ground has been reduced, and the reduction must increase proportionately
as the strength of the wind increases and forces the balloon still more
towards the ground. At the same time, owing to the tilt given to the
car, observation is rendered more