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42 the centre of the square. Metallised paper is stretched across the framework and secured to it by glue.

German meteorological balloons are generally made of natural-coloured rubber with a non-fabric strengthener, or are made of latex. They have a peculiar smell which is quite distinct from that of their British counterpart. They can be definitely distinguished, however, by the fact that they are constructed in several segments, whereas British balloons are all in one piece or in two sections; again, German balloons have a number of rubber loops cemented on with strings attached to hold the instruments, whereas British balloons have the instruments tied to the neck or valve.

The German balloon measures about 4 ft. long when deflated and weighs from 1 to 2 lb. The Germans have also used balloons of French manufacture, similar in construction to the British type. The distinguishing features mentioned above may, therefore, not always be present.

All such balloons, both British and German, are liable to leak, in which case they may come to the ground still partially filled with hydrogen.

No naked light or lighted cigarette should be brought too near them otherwise the gas may ignite, or, in the case of larger balloons, cause an explosion.

Apart from the danger of fire, hydrogen is harmless.

18. LEAFLET-CARRYING BALLOONS

Two types of German leaflet-carrying balloons have been found so far, one khaki and the other silver, but apart from colour they appear identical. As will be seen from the illustration (Figure 62), they are in the form of a vertical cylinder with rounded ends, and measure when deflated about 16 ft. by 13 ft. They are made of rubberised fabric and have a long fin of some 4 to 5 ft. at the base.

The leaflet-carrying box is slung underneath, and consists of a small cardboard box in cube form with an 8½ in. side, in the centre compartment of which is a simple clockwork mechanism. Around this are four compartments (see Figure 63), containing bundles of leaflets which are held in position by wire bands until the moment of release.