Thereupon, on his return to Stockholm, he carefully tested the samples which he had brought with him; he felt interested in the English and German products, but gave preference to the French industry. Finally his choice fell on Chinese Pongee silk, cemented together in double, threefold, and fourfold layers, and varnished, this tissue having been advocated and experimented with for several years past by M. H. Lachambre, to whom Andrée entrusted the construction of the balloon on condition that M. Lachambre should follow the expedition to Spitzbergen, where the benefit of his experience would be at Andrée’s service.
The Aerial Vessel
Description of the Balloon for Andrée’s Polar Expedition, and the Appliances Constructed at the Aerostatic Workshops of Vaugirard.
After studying the question for a long time, Andrée finally decided to give his balloon the cubical contents of 158,924 feet, and the shape of a sphere terminating in a slightly conical appendage.
This sphere, fitted with two lateral regulating valves, one lower automatic valve, and a “rending flap,” measures 22 yards in diameter, by 1,431 yards surface; it is enclosed in a net of hemp cord, terminating in systems of “crow feet,” and suspending ropes attached to the car by means of a “load ring.”
The upper part of the balloon is protected against rain and snow by a varnished silk cover, the apex of which is fixed to the upper pole of the envelope, and the lower margin to the meshes of the net.
The Envelope.—In making up the envelope, 600 pieces of best quality Pongee silk, each from 18 to 19 yards long by about 18 inches wide, were used. From each of these a piece was cut off which was tried in both directions—that of the chain and that of the weft; then the pieces were classified according to their strength, in order to be subjected to the operation of cementing or joining together.
All these pieces, after being cemented together, were tried again before being used. The trials were made by means of a Perreaux dynamometer, with strips about 2 inches wide by 4 inches long, under the control of Messrs. P. de Nordenfeld and Noël, engineers of the Nordenfeld Company, to whom Andrée had entrusted the task of testing the materials used in the construction of his balloon.