446 



SCIENCE 



[N. S. Vol. LI. No. 1323 



shipment in the amount of 14,000 ship 

 tons a month, but had it been possible to 

 use single conductor bare wire in place of 

 the twisted pair insulated wire, the space 

 required would have been reduced to 2,500 

 ship tons a month, thus releasing the bal- 

 ance for transportation of food, and other 

 vitally necessary supplies. 



It is therefore of paramount importance 

 to diagnose, as far as possible, the tech- 

 nical problems of equipment in the light 

 of past esperience and of the present 

 trend of development. 



The above facts show the necessity of 

 developing, if possible, new methods by 

 which a reduction may be effected in the 

 enormous quantities of expensive and 

 bulky insulated wire, which was so diffi- 

 cult to procure, and w'hich must now be 

 iburied in the earth to a depth of 8 or 10 

 ifeet throughout the advance sectors of the 

 front line of a modern army. 



THREE MEDIA FOR ELECTRIC WAVE 

 PROPAGATION 



The following reasoning led to the carry- 

 ing out of the experiments to be described : 



1. Since we can already communicate by 

 radio means between one submarine and 

 another submarine, both completely sub- 

 merged, it was considered that connecting 

 two such stations by a submerged copper 

 wire could have no other effect than to 

 facilitate the propagation of the electric 

 waves between the stations. 



2. It was considered possible that the 

 behavior of earth or water under the 

 action of high frequency currents might 

 exhibit greatly different properties from 

 those with wihich we are familiar at direct 

 or low frequency currents. 



3. It was realized that whatever high 

 frequency energy losses might occur in 

 the ease of bare wires laid in earth or 

 water, yet the over-aU efSciency would be 



higher than in the case of radio space 

 transmission where the plant efficiency is 

 so very low. 



4. It was noted by the writer in Septem- 

 ber, 1910, and discussed by him in April, 

 1912,^ that the three-electrode audion 

 could be used as a potentially operated 

 device on open circuits. This arrange- 

 ment was considered suitable for the 

 reception of the signals over bare wires in 

 earth or water. 



PRELIMINARY EXPERIMENTS 



The first experiment was an extremely 

 simple one as follows : A bare No. 18 phos- 

 phor bronze wire, such as is used for the 

 Signal Corps field antenna, was laid across 

 the Washington Cliannel of the Potomac 

 River from the War College to the op- 

 posite sliore in Potomac Park. It was 

 paid out from a small boat with sufficient 

 slack to lay on the bottom of the river. 

 A standard Signal Corps radio telephone 

 and telegraph set, SCR 76, was directly 

 connected to eadh end of the wire, one set 

 serving as a transmitter and the other as 

 a receiver. At the receiving end of the 

 line the bare wire was directly connected 

 to the grid of the receiving set and the 

 usual ground connection left open. A fre- 

 quency of about 600,000 cycles a second 

 was used and the line tuned at each end 

 by the usual methods. Excellent teleg- 

 raphy and telephony were obtained. Care 

 was taken to make this preliminary experi- 

 ment as simple and basic as possible and 

 precaution taken to insure that the wire 

 itself should be brigiht and clean entirely 

 free from any grease or other insulating 

 material. 



2 Journal of The Franklin Institute, Aprfl 1, 

 1912, "Some Experiments in 'Wired Wireless' 

 Telegraphy for Field Lines of Information for 

 Military Purposes," by Major George O. Squier, 

 Signal Corps, U. S. Army. 



