All About Inventions and Discoveries
The Romance of modern scientific and mechanical Achievements

244 All About Inventions a metallic girder skeleton over which was stretched the fabric or skin. Instead of this envelope, as it may be called, being charged with gas in the usual manner—such as a balloon—the interior was sub- divided into a number of compartments insulated from one another by a thin wall or diaphragm of fabric. Consequently, the interior of the skin be- came resolved into a number of cells, and in each of these was placed a balloon inflated with hydrogen. The balloons themselves favoured the conventional spherical form, so that the whole of the cell was not occupied by the gas-bag. This arrangement was adopted because it left a space around the gas-bag through which the air was free to circulate. It was maintained that this arrangement would render the gas-bag less susceptible to the fluctuations of tempera- ture, which cause the hydrogen to expand and to contract respectively, according to heat and cold. It will be seen from this subdivision, which is still practised, that the interior of a Zeppelin resembles very closely the interior of a ship which is subdivided into watertight compartments by the aid of bulkheads. In the first vessel there were no fewer than seventeen of these compartments, each containing its individual inflated gas-bag. One advantage of this system of construction was pointed out—in the event of one gas-bag being damaged, and its gaseous contents escaping, the descent of the balloon to the ground did not necessarily follow. It would merely cause the vessel to sink to a lower altitude. As a matter of fact, a certain number of the compartments would require to be damaged before the airship was compelled to come to the ground.