HIGH-SPEED OCEAN CABLE TELEGRAPHY 235 



the conductor and also forms a layer a few thousandths of an inch 

 thick on the outside of the loading material. The gutta-percha 

 insulation may then be extruded over the impregnated conductor 

 with the assurance that the semi-fluid compound will serve to equalize 

 the pressure on the permalloy. Numerous compounds have been 

 proposed and used for this purpose, that on the New York-Horta 

 cable being of an asphaltic type. It is essential, of course, that this 

 compound be sufficiently viscous at temperatures at which the gutta- 

 percha is applied to permit extruding the gutta-percha around it and 

 that it will also be sufficiently fluid at the temperature of the sea 

 bottom, which may be as low as 2° C, to permit readjustment of 

 the pressure on the permalloy. When a loaded conductor insulated 

 in this manner is subjected to high pressures at low temperatures, it 



Fig. 3 — Permalloy-loaded cable. Above, section of deep-sea type from New York- 

 Horta cable. Below, section of core showing permalloy tape partly unwound 



may be found that the inductance drops when the pressure is first 

 applied but in a few minutes the compound flows so as to equalize 

 the pressure on the permalloy and the inductance quickly comes back 

 to its original value. 



Outside of the insulated conductor or "core" of the cable the 

 permalloy-loaded cables which have been made are quite like ordinary 

 non-loaded cables, so there is no need to go into the further details of 

 cable construction here. Fig. 3 shows a section of the deep-sea portion 

 of the New York-Horta cable. 



Principles of Design of Loaded Cables 



There are two principal aspects of the design of a submarine cable — 

 mechanical and electrical. Mechanically, the cable must be so 

 designed as to insure that the conductor shall be continuous, that its 



