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The lower zone, terminating the protecting cover, is of double silk. Its extreme edge is put round a hemp bolt-rope, ³⁄₁₀ inch in diameter, which is sewn into the material; ninety-six eyes made above this bolt-rope are intended to receive thongs for fixing the protecting cover to the meshes of the net.

This protecting cover weighs 88 lbs. Its object is to protect the top of the balloon against rain, and more especially to prevent incrustation with snow between the meshes of the net.

Valves.—The balloon has no valve at the top, because its action would probably be affected by snow; but it is provided with two manipulating valves, of equal dimensions, one being placed at the equator, and the other one metre above the equator. These are at 150 degrees angular distance from each other.

These valves, constructed on a system of Andrée’s, measure 9⅘ inches in external diameter. Each is formed by a disc of aluminium bronze, 9 inches in diameter, and under normal conditions rests on a circular piece of walnut wood, but can be withdrawn therefrom by moving it along a screw which occupies the centre. This movement is effected from the car of the balloon by means of two cords for each valve, passing through the interior of the balloon and issuing from it near the appendage through four tubes, arranged in pairs.