It was not until 1872 that he finally secured the building of an airship, at Vienna, after his plans. It was 164 feet long, and 30 feet in diameter. The form of the gas-bag was that described by the keel of a ship rotated around the centre line of its deck as an axis. The engine was of the Lenoir type, with four horizontal cylinders, developing about 6 horse-power, and turned a propeller about 15 feet in diameter at the rate of 40 revolutions per minute. The low lifting power of the coal gas with which it was inflated caused it to float quite near the ground. With a consumption of 250 cubic feet of gas per hour, it travelled at a speed of ten miles an hour. The lack of funds seems to have prevented further experiments with an invention which was at least very promising. [Illustration: Sketch of the De Lome airship.] In the same year a dirigible balloon built by Dupuy de Lome for use by the French Government during the siege of Paris, was given a trial. It was driven by a screw propeller turned by eight men, and although it was 118 feet long, and 49 feet in diameter, it made as good a speed record as Giffard’s steam-driven airship--six miles an hour. [Illustration: Car of the Tissandier dirigible; driven by electricity.] In 1881, the brothers Albert and Gaston Tissandier exhibited at the Electrical Exhibition in Paris a model of an electrically driven airship, originally designed to establish communication with Paris during the siege of the Franco-Prussian War. In 1883, the airship built after this model was tried. It was 92 feet long, and 30 feet at its largest diameter. The motive power was a Siemens motor run by 24 bichromate cells of 17 lbs. each. At full speed the motor made 180 revolutions per minute, developing 1½ horse-power. The pull was 26 lbs. The propeller was 9 feet in diameter, and a speed of a little more than 6 miles an hour was attained. [Illustration: Sketch of the Renard and Krebs airship _La France_, driven by a storage battery.] In 1884, two French army engineers, Renard and Krebs, built an airship, the now historic _La France_, with the shape of a submarine torpedo. It was 165 feet long and about 27 feet in diameter at the largest part. It had a gas content of 66,000 cubic feet. A 9 horse-power Gramme electric motor was installed, driven by a storage battery. This operated the screw propeller 20 feet in diameter, which was placed at the forward end of the long car. The trial was made on the 9th of August, and was a complete success. The ship was sailed with the wind for about 2½ miles, and then turned about and made its way back against the wind till it stood directly over its starting point, and was drawn down to the ground by its anchor ropes. The trip of about 5 miles was made in 23 minutes. In seven voyages undertaken the airship was steered back safely to its starting point five times.