1914 1915 1916 1917 1918 Total At Friedrichshafen 6 19 14 14 8 59 At Potsdam 1 7 8 — — 16 At Staaken — — 2 9 1 12 At Frankfort on Main 1 .. .. .. .. 1 __ __ __ __ __ __ Total 8 26 24 23 9 88 [PLATE 25: Zeppelin-Dornier “Dragon Fly” All Metal Flying Boat, 1921. Wing span, 28 feet, weight empty 858 pounds. Water tight bulkheads are provided in-side fins and wings. Zeppelin-Dornier “Dragon Fly” All Metal Flying Boat, 1921. With wings folded greatest width is only 10½ feet.] That in itself was a remarkable achievement which could have been accomplished only by possessing the scientific knowledge borne of experience. But it is not all. One Hundred and Fifteen Zeppelins Built and Operated From the day Count Zeppelin built his first ship until the last in 1919, a total of 115 Zeppelins were built and operated. The first three were experimental. Nine Zeppelins were successfully operated commercially in the transportation of passengers. Forty were delivered to the German army and 63 to the navy. Scientific Comparison There exists in the field of engineering an impartial, positive and unswerving means of determining the relative merits of things; and that is by a technical analysis of their success. By it one may recognize the values of the principles and construction methods involved. It is commonly said that nothing succeeds like success; and this is virtually true of the Zeppelins. Their record for efficiency remains unsurpassed, as a matter of fact, unequalled. It has never been denied that they were superior to contemporary craft or that they failed to maintain an increasing advantage over them. This comparison is justified by the following figures which we will first attempt to explain. It will be noted that there are three kinds of efficiency, (1) Speed (the aerodynamical figure), (2) Lift (the constructional figure) and (3) All-around efficiency (the combined quality figure). The first relates to the efficiency of airship propulsion as effected by degrees of refinement in form, lessening of resistance, conservation of power, etc. It is simply the relation between the speed and engine power. Inasmuch as higher speed with the same power or the same speed with less power means economy of operation; therefore, the higher figure indicates superior quality. [PLATE 26: Zeppelin-Dornier “Dolphin” Monoplane All Metal Flying Boat Type DoCsII, 1920 Model. Zeppelin-Dornier “Dolphin” Monoplane All Metal Flying Boat Type DoCsII, 1921 Model. Carries six passengers besides pilot and mechanician. Speed 93 miles per hour, 185 horsepower motor. Gasoline consumption 11.9 gallons per hour. Weight empty 3200 pounds.]