CONQUEST OF DISTANCE BY WIRE TELEPHONY 357 



formally with the Long Lines plant people, no suitable types of additional 

 new facilities were in prospect, in consequence of the somewhat slow re- 

 covery of general business activity following the 1907 panic. Prior to start- 

 ing production of the new types of coils, models were turned over to the Long 

 Lines telegraph experts for tests to determine whether objectionable im- 

 pairment in the superposed telegraph service would result in consequence 

 of the increased magnetic coupling between the telegraph circuits, con- 

 tributed by the loading coils. The favorable report on this feature was 

 tinged with an informal suggestion of regret that the wide application of 

 phantoms in the long distance plant would reduce the aggregate number 

 of wires that would be available for the leased wire telegraph services. 



In arranging for potting the loading coils used in the trial installation, 

 the decision was made to encase the coils individually so that in the event 

 of unsatisfactory results the phantom loading could be removed without 

 disturbing the side circuit loading. The phantom coil was considerably 

 larger than the side circuit coil, and a new case had to be developed for it. 

 The practice of separate potting of the individual coils continued for several 

 years, mainly for fiexibiHty and maintenance reasons. Not long after the 

 trial installation, the manufacture of the non-phantom type open-wire 

 loadmg coils was discontinued in favor of the new side circuit type. Gradu- 

 ally, the bulk of the existing non-phantomed loaded circuits m the open- 

 wire plant was made suitable for phantom working. The displaced non- 

 phantom type loading coils were returned to the factory for "conversion" 

 into side circuit type coils, by partial rewinding of the original cores. 



Loading of 165 Mil Open- Wire Circuits 



The development efforts to improve the wet weather insulation of 165 

 mil wires sufi&ciently to make loading commercially practicable culminated 

 in an experimental installation of loading on a New York-Chicago circuit 

 during 1909 and early 1910. 



The initial steps in this trial were (a) to change the transposition arrange- 

 ments from the single-pin type to the drop-bracket type in order to avoid 

 tying to the same insulator the two wires being transposed, and (b) to install 

 bridle wire insulators at all bridling points, including the loading coil and 

 lightning arrester leads. Comparative wet weather tests of the single-pin 

 and the drop-bracket transposition arrangements made previously had 

 indicated the new method to be about 20 per cent better, and tests with the 

 bridle wire insulators had indicated their use would substantially eliminate 

 low insulation at bridling points. 



The bridle wire insulator was the final result of a long period of develop- 

 ment. It provided sheltered dry spots on the rubber-insulated braided leads 

 of loading coils and lightning arresters, and on bridle wires to test stations 



