In 1900, Count von Zeppelin’s great airship, which had been building for nearly two years, was ready for trial. It had the form of a prism of 24 sides, with the ends arching to a blunt point. It was 420 feet long, and 38 feet in diameter. The structure was rigid, of aluminum lattice work, divided into 17 compartments, each of which had a separate gas-bag shaped to fit its compartment. Over all was an outer envelope of linen and silk treated with pegamoid. A triangular keel of aluminum lattice strengthened the whole, and there were two cars of aluminum attached to the keel. Each car held a 16 horse-power Daimler gasoline motor, operating two four-bladed screw propellers which were rigidly connected with the frame of the ship a little below the level of its axis. A sliding weight was run to either end of the keel as might be required to depress the head or tail, in order to rise or fall in the air. The cars were in the shape of boats, and the ship was built in a floating shed on the Lake of Constance near Friedrichshafen. At the trial the airship was floated out on the lake, the car-boats resting on the water. Several accidents happened, so that though the ship got up into the air it could not be managed, and was brought down to the water again without injury. In a second attempt a speed of 20 miles an hour was attained. The construction was found to be not strong enough for the great length of the body, the envelope of the balloon was not sufficiently gas tight, and the engines were not powerful enough. But few trips were made in it, and they were short. The Count set himself to work to raise money to build another ship, which he did five years later. [Illustration: View of the Zeppelin I, with portion of the aluminum shell and external fabric removed to show the internal framing and separate balloons. In the distance is shown the great balloon shed.] In 1901, an inventor named Roze built an airship in Colombo, having two gas envelopes with the engines and car placed between them. He expected to do away with the rolling and pitching of single airships by the double form, but the ship did not work satisfactorily, ascending to barely 50 feet. In 1902, Augusto Severo, a Brazilian, arranged an airship with the propelling screws at the axis of the gas-bag, one at each end of the ship. Instead of a rudder, he provided two small propellers to work in a vertical plane and swing the ship sideways. Soon after ascending it was noticed that the propellers were not working properly, and a few minutes later the car was seen to be in flames and the balloon exploded. Severo and his companion Sache were killed, falling 1,300 feet. [Illustration: Sketch of the Severo airship, showing arrangement of the driving propellers on the axis of the gas-bag, and the steering propellers.] [Illustration: