Page:Popular Science Monthly Volume 88.djvu/513

 Popular Science Monthly

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��larger dirigible, for it loses the greater lightness for the same strength of a small structure. In a small dirigible resistance against propulsion is so much greater than the lift available for engine power in the large craft, that it com- pletely discounts the small craft's struc- tural advantages. Any improvements in lightness and strength will, therefore, never make this pigmy Zeppelin a superior in speed to its larger and more powerful rival.

The whole idea of a small and speedy "aerial destroyer" is mistaken, since in a dirigible everything has to take second place to speed; otherwise Zeppelins,

��crease the lifting power, and consequent- ly the size, in order to achieve greater power and speed. Whether the Zeppelin has been a success or not is a mooted point, but the Zeppelin has been the only dirigible that has accomplished anything of note in this war, and the smaller dirigibles have been permanently relegated to their hangars.

A Barbed-Wire-Proof Fabric

ONE of the most trying tasks incident to trench fighting has been consid- erably lightened by the appearance in the British trenches of gloves made of a fabric which is said to be imper\ious to

���13 DRUMS OF HYDROGEN GAS KEEP THE CRAFT ALOFT

The designers believe that the laminated wood con- struction will produce an airship which is one-third lighter than a Zeppelin could be built with similar dimensions. Two sixty-horsepower motors drive four propellers, and the airship will be expected to make more than seventy miles an hour at full speed

��DIRECTION •RUDDER

��which cannot seek safety in landing, would be at the mercy of the wind.

The rope drive to the propellers has been proved greatly inferior to bevel gearing, chains and belts. The cable drive was tested on the first Gross- Basenach, but was quickly discarded.

The most meritorious feature of the design of the pigmy Zeppelin is in the alternate heating and cooling of the gases by hot vapor from the engine and cool air sucked in by blowers. This certainh' should i)rove of valuable assistance to the dynamic lift-control without en- tailing much additional weight.

In conclusion, it seems that the idea of a wooden frame has been tried, ap- proximately in its present form, and found lacking. The rope drive has been succeeded by more efficient means of power transmission, and the entire trend of dirigible construction has been to in-

��barbed- wire points. The fabric is made up into mittens, with the first finger and thumb separate. The fabric is water- proof, and in addition the gloves are insulated for gripping electrically- charged wires.

The same material is applied to the manufacture of sleeping-bags, which, when opened, may be thrown o\er a barbeJ-wire entanglement to allow a soldier to climb over the sharp points without injury. When made up into \'ests or tunics, the fabric is strong enough to turn shrapnel splinters, or even a bullet when it has lost part of its momentum. The interlining is anti- i;epticized, so that if a bullet goes through, it takes into the wound enough antiseptic wool to prevent poisoning.

The materials used in the manufacture of this reniarkal)le fabric ha\e been sedulously kept secret this far.

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