Page:Popular Science Monthly Volume 92.djvu/602

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��Popular Science Monthli/

��New Method of Mounting Un- breakable Watch Crystals

TO overcome the inevitable loosening of the crystal in watches suitable for soldiers' wear one manufacturer clinches the rim into the crystal as shown in the accompanying illustration. The crystal employed is likewise made of a compound that will not burn, thus forming an ideal device for wear in the open or where the watch is liable to receive hard knocks.

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���This crystal is clamped into the watch rim to prevent loosening

��Acetylene Trench Gun — It's a Great Thrower of Shells

ACETYLENE gas does not work well . as an engine fuel. It is too ex- plosive. However, a Paris inventor, R. A. Brevaire, would turn this to good use in a trench-gun.

The lower part of his machine consists of a chamber into which air is forced under pressure, or sucked in by the rush of an outgoing shell. Hav- ing thus filled the cham- ber with air, the operator next admits a small quantity of acetylene gas by means of a valve. Air and the gas intermingle forming a highly explo- sive mixture. This is set off at will by means of a spark plug and a suitable coil. Shells are inserted in the gun by dropping them through the muzzle, rear-end foremost. If the gun-barrel is unrifled, wings at the base of the shell make it spin and fly true. A sound-deadening chamber is fastened to the outer end of the gun; it is built on the principle of an automobile muffler.

This gun is new in being the first trench gun to use gas as an explosive.

��Poisonous and Harmless Mush- rooms Difficult to Distinguish

N a special bulletin published by the U. S. Department of Agriculture special emohasis is laid upon the fact that there is no simple test for distinguishing between edicle and poisonous mushrooms. Many of the alleged distinguishing marks used by farmers, dealers and purchas- ers of mushrooms to differentiate between edible and poisonous mushrooms are con- sidered by the ex- perts of the Depart- ment entirely fallacious or too unreliable to be used with safety. The only safe mushrooms to eat are those gathered by a collector who knows exactly what he is doing. Only such mushrooms should are known to be non- all mushrooms, which in any way differ from the known type of edible va- rieties should be left severely alone. Every season there are numerous fatalities from eating the poisonous varieties.

��Diagram and illustration of a new acetylene trench mortar, fitted with silen- cer and recoil mechanism. Acetylene is too explosive for automobiles, but this is a virtue in guns

��be picked as poisonous and

��Silencer

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