444 



Popular Science Monthly 



Spark gap- 1 



The operator's set comprises a four-inch spark coil, a manipu- 

 lating key, and a small fixed oil condenser, all in a steel box 



As you might Imagine, the set is small 

 and extremely light. It comprises just a 

 4-in. spark coil, a manipulating key, a small 

 fixed oil condenser, contained in a steel box, 

 and an aerial coil. This helix or aerial 

 coil is not made of the usual copper tubing, 

 bound on a wooden frame. It is made of 

 several turns of soft flexible insulated wire 

 wound round a piece of wood and kept se- 

 curely in place by two cross-pieces of wood. 



The lay-out of the appa- 

 ratus is not 

 necessarily 

 uniform. 

 Usually the 

 airman shifts 

 it to suit his 

 own con- 

 venience, but 

 as a rule its 

 position is 

 this: The 

 condenser 

 and coil are 

 placed under the seat; the aerial coil is 

 made fast to the framework near the 

 operator. The key is on a small wooden 

 shelf fixed to the side of the seat, and 

 sometimes it is placed on a partition in 

 front of it. 



In the case of the small scouting ma- 

 chines, the aerial is fixed on the top of the 

 wings and runs round the edge, while the 

 lead-in wire is brought in from the center. 

 Then the earth or ground wire hangs over 

 the side of the plane to the same length and 

 capacity as the aerial. In these cars, of 

 course, the pilot and operator are identical. 

 Only one man goes up. 



In the big battleplanes, the aerial is in 

 much the same position. It is fixed to the 

 top. of the top plane. But the ground wire 

 is arranged differently from that on the 

 scout machines. Here it is attached to the 

 bottom of the bottom plane. In other 

 words, there is an upper and lower capacity, 

 just as in the Lodge-Muirhead system. 



Now in these planes the operator is the 

 observer. He sits in front of the pilot. 

 But, in case he should be shot or in any way 

 incapacitated,, there is a manipulating key 

 in the pilot's pit joined in parallel to that in 

 the observer's chair, so that either man is in 

 a position to operate. 



There is, of course, no receiving ap- 

 paratus. So far it has not been found 

 necessary. For if you are traveling at the 

 rate of 120 or 130 miles an hour, which is 

 the speed many of these planes are able to 



make, it is hard enough to breathe without 

 wasting effort in trying to hear. Besides, 

 even if the rush of air would permit you to 

 collect your senses, there is still the 

 propeller to be reckoned with. The noise 

 of this close to the ear can be compared only 

 with that of a forty-coach express train 

 tearing at top speed through a tunnel. 



But suppose it were possible to perfect an 



instrument that could make itself heard 



against these handicaps, of what use 



Glass would it be, 



when com- 

 p 1 e t e d ? 

 Under the 

 circum- 

 stances in 

 which the 

 airman 

 fights, in- 

 struc tions 

 from the 

 earth are of 

 nousetohim. 

 He is the one man in the war who fights as 

 an individual. Once he has left the earth 

 with general orders as to the object of his 

 flight, he takes advice and instruction from 

 no one. The thoroughness of his work, the 

 chances of his safety are matters left 

 entirely to himself. They depend solely on 

 individual initiative. 



Let me take you with him on a trip, 

 typical of one he might make any morning 

 that is clear enough to let him see what is 

 happening on earth. 



Oil condenser- 



Aerial coil-^ 



"VL—O'i condenser 



The condenser and coil are placed under 

 the seat and the key on a shelf near by 



The artillery has got the range roughly 

 and set their sights accordingly. The air- 

 man ascends, and is soon soaring over the 

 enemy lines. Now he is in sight of the 

 target. 



He signals "G" back to the artillery. 

 That means "Go ! Commence firing." 



They fire. In a couple of seconds there 

 ascends a streak of smoke. To his eye it is 

 no bigger than the puff of a cigarette, but it 



