Page:Popular Science Monthly Volume 89.djvu/20

 Popular Science Monthly

��four directions at once, but with difTerent intensities, the pencil will rest at that point where all the forces are equalized. That point, in the case of the precision indicator, is the spot in which the hostile vessel is to be found.

Imagine New York Harbor mined and microphoned in the manner that 1 have described; imagine the mines ((jnnected with a luminous annunciator at Fort Wadsworth and with a precision indicator provided for the purpose of determining which microphone in a square hears the most; imagine a submarine crawling very, very cautiously through the field, thrusting aside with careful antenna, the anchor-chains of the buoyant mines in its path. An American officer glues his eyes on the luminous board. One by one the squares glow before him — 19, 36, 53, 66. Unwittingly the submarine's commander plots his course in a trail of light. He cannot be seen with human eyes; and yet he is as visible, electrically at least, as a goldfish in a glass bowl. "Square 78," says the American officer to himself, as a new light flashes up. The time has come for decisive action. He j)ulls a handle and switches the precision indi-

��cator into electrical connection with square 43. The submarine is nearest mine "A" of that unit, for the micro- phone on mine "A" is intensely active. He presses a button. Miles away a column of water is tossed into the air. An unseen enemy has been destroyed with awful suddenness; twenty brave sailors have been killed with merciful swiftness by a man who never saw their faces.

The naval and military strategist will note at once that the system which I have described has this advantage over the rather haphazard method of utilizing the contact mines at present employed. It renders it possible to destroy a whole fleet, ship by ship, as it progresses into a harbor which is protected. The officer at the luminous indicator board has only to wait until the lamps show that the entire .squad- ron has entered the field to blow up ship after .ship at his pleasure. It is also apparent that the system is not limited in its application to the de- tection of battleships or submarines in a mine-field, but that it can also be adapted to the firing of coast-defense sh{)rc-i)atlcries.

��Automobile Scale-Demonstrator

��ON the principle that if you can't get the buyer to come to you, you will have to take your product to the buyer, a large man- ufacturer of scales for weighing grain recently fitted up one of his scales on a light automobile and sent it out through several of the western state's as a demonstrator. As shown in liic a c c o m p a n y i n g illustration, the car was fitted with a complete scale and in addition a port- able elevator to

���An automobiU- usid for dimonstrntiiis

scalts. Thf owntr trnvds from town to

town, the scale enclosed in canvas and the

portable elevator carried on the side

��raise the grain to the former, so that it really was a working model for t he prospec- tive buyer to in- spect.

The car travels from town to town, the scale proper being enclosed in c.invas enroute anif the portaiile eleva- tor is carried on the side. The power for driving the elevator is secured from the motor of the automobile.

The money-mak- ing ability of this outfit has been clcarlv shown.

�� �