98 Professor J. A. Fleming [March 27, 



having the greater store of energy would go farthest because it has 

 more energy to expend in overcoming water friction. So also is it 

 with the electric waves in the cable. We have to consider in tele- 

 phone engineering the three cases of aerial or overhead lines, 

 underground cables, and submarine cables, and it may be well :it 

 this point to say a few words as to the manner in which these 

 three kinds of lines are now loaded, or " Pupinized " as the French 

 call it. 



In the case of overhead lines the inductance coils are included in 

 iron boxes, which can be attached to the telegraph posts at the 

 proper interv;ds. (See Fig. 5.) 



For underground lines they are put in iron boxes in pits and the 

 coils for a large number of lines can be placed in the same pit. (See 

 Fig. 6.) 



The type of cable now used for urban and underground work is a 

 cable called a dry core cable, in which each wire is insulated by 

 twisting loosely round it a strip of dry paper, and numerous pairs of 

 such wires are enclosed in a lead sheath drawn over them. The 

 insulation of each wire is thus really air and paper, and the advantage 

 of this is much smaller value of the capacity compared with a wire 

 insulated with gutta-percha or indiarubber. 



The conduits in which these cables are run have to be kept dry 

 by passing dry air through them. 



The problem of loading a submarine cable with Pupin coils 

 presented greater difficulties both in construction and in laying. 

 These difficulties were overcome with great success after much 

 preliminary research by the scientific staff of Messrs. Siemens Bros., 

 and in the Engineering Department of the General Post Office 

 when under the able control of Major W. A. J. O'Meara as Engineer- 

 in-Chief. 



Two such loaded cables have now^ been laid across the English 

 Channel from England to France, and to Belgium for the British 

 Government, and also another type of loaded cable has been laid 

 by the French Administration close to one of the above cables between 

 France and England. A coil loaded cable has also been laid by 

 Messrs. Siemens Bros, for the General Post Office across the Irish 

 Channel, under the direction of the present Engineer-in-Chief, Mr. 

 W. Slingo. 



The problems to be solved in successfully making and laying a 

 loaded submarine telephone cable were partly electrical and partly 

 mechanical, and required the greatest experience and knowledge to 

 grapple with them. 



As regards the cable laid in 1910 between England and France 

 from Abbots Cliff to Grisnez, the full details of all the previous 

 researches and of the structure and laying of this cable have been 

 described in an admirable and most valuable paper by Major W. A. J. 

 O'Meara, C.M.G., at that time Engineer-in-Cbief to the General Post 



