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. 



