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Gas-tightness is obtained by a circular rubber band, against which the outer margin of the valve disc rests. The orifice for the escape of gas measures 7⅘ inches in diameter. In order to fix the valves to the balloon, two openings, 7⅘ inches in diameter, are made in the material. The margin around these openings is strengthened by collars, 19⅖ inches in diameter, of threefold material, cemented and sewn on; the seat of each valve is applied internally to the material of the balloon, the margin of which is caught between two rubber bands, and thereupon pressed against the seat by an external wooden hoop and bolts.

These valves do not present any external projection against which the cord of the net might catch.

The automatic valve closing the appendage was suggested to Andrée by M. Lachambre, and was adopted. It measures 39 inches in external diameter, with a discharge orifice 34 inches in diameter. The valve disc, of threefold Pongee silk, is 35⅘ inches in diameter. It is provided with two glazed windows, in order to enable the aeronauts to inspect the interior of the balloon. This disc, which is slightly conical, is fitted upon a walnut-wood ring, which acts as a seat, in which it is held by the traction of six spiral springs of steel wire, fastened on one side to the end of the wooden spokes of the valve, and on the other side to the top of a small frame fixed on the seat. The frame, mounted on the wooden ring or crown, is formed by twelve nickeled steel tubes.