314 



Popular Science Monthly 



further improbable. The thickness of 

 the mica sheets has been so proportioned 

 to those of the metal leaves that when a 

 hole is burnt through the dielectric, a 



Construction of the casing for a conden- 

 ser with lead-in terminals attached. The 

 dotted line shows the protective cover 



larger hole is burnt through the foil. 

 Hence, in this condenser, two oppositely 

 charged pieces of foil cannot come 

 together through the hole made by the 

 leaking currents. The condenser is truly 

 eelf-healing. 



As a last precaution against its being 

 burned out by a short circuit, the gen- 

 erator has the pair of protective con- 

 densers shunting it. For these condensers, 

 the Navy officials have also adopted a 

 Dubilier invention, in which two of their 

 condensers are placed. Besides its re- 

 liability, the Dubilier device is also fool- 

 proof. For, as the diagrams show, should 

 their condenser be removed from the 



GENERATOR 



Hook-up showing positions of condensers 

 in the line and how the connections 

 would not be complete without them 



circuit, the generator connections would 

 not be complete until another box of 

 protective condensers is connected with 

 the circuit. 



Increasing the Range of the Ground 

 Wireless Station 



IN experimenting with inductive coils, 

 placing them with the buzzer in the 

 ground circuit, to see if increasing the 

 inductance would not send larger currents 

 into the earth, it was found that the 

 sending range could be increased in this 

 way to a considerable extent. 



First, the contact connections of the 

 buzzer were changed as shown in the 

 diagram. The secondary of the sending 

 coil was connected between the buzzer 

 contact and the buzzer coils, and to vary 

 the inductance, the laminated iron core 

 was moved in and out. For some stations, 

 of course, the ordinary variable radio 

 loading coil will do the trick just as well. 



Naturally, the sending range will be 

 largest when the buzzer is vibrating well 

 and the maximum current is sent into the 





Considerably increasing the sending range 

 of a ground wireless station, by the use of 

 an induction coil placed with the buzzer 



ground. Therefore the inductive coil 

 should be tuned as in radio work, until 

 the ammeter in the earth circuit registers 

 the largest current. — E. T. Jones, Chief 

 Electrician, Radio, U. S. N. R. F. 



Where Fiber May be Used as a Fire- 

 proof Material 



FIBER is an almost fireproof material. 

 Almost — for it will burn. But, un- 

 less it is kept on fire by some outside 

 source it will go out, and it requires a 

 very hot flame to ignite it. So, when 

 anyone wants to use fiber in a situation 

 exposed to heat, he can do so. There is 

 little danger of its burning except when 

 it is in the direct path of a flame. The 

 close texture of this material prevents a 

 flame from taking hold unless forced by 

 a draft. 



