Sharply pointed stern with “tail” and rudders like those of an aeroplane. IT is only recently that the true significance of the great dirigible dockyards in Friedrichshafen became alparent. From the early summer of 1910, till the spring of 1911, no new airship left the stocks, and when finally a second “Deutschland” put in an appearance, she looked like a mere reconstruction, showing neither greater speed nor better maneuvering qualities than the first “Deutschland,” which had been shipwrecked the year before. Still there was progress in a less conspicuous but very important direction. The first “Deutschland” had come to grief because under very adverse conditions and with a motor failing at the most critical moment, she could not be l,ept afloat, and gradually settled into the. pine trees covering the crest of the Teutoburger Wald mountains, which she had to cross at that time. To strengthen the new “Deutschland's” floating power in any similar emergency, her hull was built lighter, permitting her to carry more ballast for the same number of passengers. In addition a special test was made over Lake Constance, to show the exact amount of the lifting and depressing effect that could he obtained from her propellers and rudders alone. It was found that with only two motors and two propellers in action, the new ship could be raised by power like an aeroplane, from a static level of equilibrium at an elevation of 2,132 feet to .4,756 feet. This represents a purely dynamic lift of considerably more than two tons (4,400 pounds). With three motors and four propellers, the ship rose fmther from 4,766 feet to 5,904 feet, adding nearly another ton (1,980 pounds) of dynamic lift. It remained for some time at this level, carrying four passengers, its regular crew of nine, 242 pounds of fuel and oil, and more than two tons (4,400 pounds) of ballast. If one,half of this ballast had now been shed, an elevation of 7,544 feet could have been reached, while still carrying over one ton (2,200 pounds) of ballast. This proves an astonishing reserve of floating power for the arrow-like Zeppelin balloons, if their motors remain intact and they are not overloaded with passengers. What it means in warfare is shown by a simple consideration. In spite of their bulk, they are safe from artillery fre at such high levels. Their diameter Is hardly greater than the wing spread of a Wright aeroplane which at the same height appears as a mere speck in the sky, and a Zeppelin at this level looks like a match, its lean shape making it a poor target. In the thin air its own speed increases; going with the strong winds of these high levels, even the slow “Deutschland” will easily surpass 60 miles an hour, making her entirely immune. Bomb dropping from aircraft becomes efficient in every respect in exact proportion to the weight of the bomb. A torpedo containing one ton of dynamite dropped from the “Deutschland” from an altitude of 8,000 feet, could be aimed with all the certainty of a shell. Air currents (and air resistance) have so little influence on this great mass that its flight through the air would be determined solely by the speed of the ship over the ground and by its altitude, both easily ascertained. Considering that a mere turn of the rudders will instantly deprive the ship of a lift of three tons, it is jeen that the suddel dropping of a Rsar car which forms the “Engine room” and holds two powerful motors. ton of ballast has no influence whatever on the stability of its flight. It seems odd that to-day the French depend so much on a costlv chain of fortresses, which might be very efficient in preventing any repetition of the sudden victorious dash of the Germans in 1870, if the tedious hauling of heavy ordnance and building of entrenched batteries were the only means of reducing them, when in the Zeppelins the Germans now possess an instrument so efficient to bombard the “key fort” without any preparation or risk, and on the sole condition of fairly good and clear weather. Although the new “Deutschland” had been amply insured against any conditions such as destroyed the frst, it was soon to fall a victim to an odd and unforeseen accident-a collision with its own shed. Trivial mishaps from lack of experience unfortunately involve a great loss of money and prestige if they happen to a large and costly dirigible instead of an inexpensive aeroplane. But in this case vindication was not long delayed. The new passenger ship “Schwaben” was almost completed whim the “Deutschland” broke in two. It was a little smaller, displacing 634,-500 cubic feet, instead of the “Deutschland's” 667,560; 462 feet long instead of 499 for the same beam of 46, and with 17 gas cells instead of 18. In spite of this handicap it showed a speed of a fraction less than 43 miles an hour in the trial trips, measured exactly by running in calm air many times in both directions, over a piece of straight railroad track of known length. As this speed exceeds that of most biplanes, and principally that of the representative Wright aeroplane, it revolutionizes all former ideas about the dirigible and its inferiority to the aeroplane. As a matter of fact the “Schwaben” \on in a race with a Euler biplane, from Darmstadt to Frankfurt. With only two of her three motors running, it still broke all previous dirigible records, at 38 miles an hour. The great improvements in Zeppelin's ships, of which the “Schwaben” was the first brilliant exponent, concern frst of all the motors. There is nothing on which the safety and success of a rigid airship depend so much as on the reliability and power of its engines. This lesson had been so well learned in Friedrichshafen that the Zeppelin factory finally undertook to design its own motors. lr. May-bach, one of their engineers, set to work improving the standard Daimler motor, which drove the earlier ships. He increased the number of cylinders from 4 to 6 and the horse-power from 110 to 165. The reliability also was so improved that the “Schwaben's” engines have never given trouble in over a hundred passenger trips, some of which were 700 miles long. Many experiments had also been made to better the shape of the hull. The difference between the “Deutschland's” conical bow and the egg-shaped bow of the “Schwaben” is striking. To diminish friction the outer envelope of the “Schwaben” was stretched very carefully over the frame. It is so smooth and firm that non-technical observers have compared the “Schwaben's” “solid” :hull to. that of a warship, on account of its “gray” color. To further cut down head resistance, the time-(Continued on page 484.)