(i.) _Zeppelin_ (German).--There are not many examples of the rigid type. The most important is undoubtedly the Zeppelin. This form of airship before the present war had elicited the interest of the aëronautical world for the long-distance records it had established. Indeed, no little sympathy had been extended to Count Zeppelin for his perseverance in the face of the gravest difficulties. Now the Zeppelin has accumulated notoriety instead of fame as having been the means of carrying on a form of warfare repugnant to the British nation, and condemned by the Hague Convention. Imagine some seventeen huge bicycle wheels made of aluminium, with their aluminium spokes complete, and these gigantic wheels to be united by longitudinal pieces of aluminium, and in this way seventeen sections to be formed, each of which contains a separate balloon, and it is easy to grasp the construction of the Zeppelin airship. It consists of a number of drum-shaped gas-bags, all in a row, held together by a framework of aluminium. They form a number of safety compartments. The bursting of one does not materially matter--the great airship should still remain in the air. The dimensions of individual Zeppelins have varied to some extent. The largest that has been built (“Sachsen,” 1913) had a cubic capacity of 21,000 cubic metres (742,000 cubic feet), and a length of 150 metres (492 feet). The aluminium framework containing the balloons has an outer covering of cloth. On each side of the frame of the airship are placed two pairs of propellers. In the original airship of 1900 these were four-bladed, and made of aluminium. They were small, being only 44 inches in diameter, but they revolved at a very high speed. In the later airships the screws have been considerably modified in detail, size, and shape. For instance, in the Zeppelin which descended accidentally at Lunéville, in France, it was found that the back pair of the propellers on each side were four-bladed, the front pair two-bladed. The screws are driven by motors placed in the two aluminium cars beneath the airship. These cars are connected by a covered gangway, which also serves as a track for a movable balance weight, by means of which a considerable change of balance can be effected. The motive power in the first Zeppelin was only two Daimler motors of 16 horse power each. With this low power little success was attained, but gradually the motive power has been increased. We find that in the naval Zeppelin, L 3, 1914. The motive power is three Maybach motors, giving total h.p. 650, whereas in the types building the total h.p. is 800.