8 THE ADDRESSES, LECTURES, ETC., OF 



water. They generally do not admit of being subdivided into 

 sections, and, therefore, a difficulty arises in regard to them which 

 does not exist in the case of shallow sea cables, respecting the 

 transmission of messages through them at a sufficient rate. 

 Another consideration is that deep-sea cables have to bear a great 

 amount of hydrostatic pressure, and we have to consider what the 

 effect of that pressure is upon the cable. Commercially speaking, 

 we may say that there is this difference between the two cables 

 that shallow sea cables, or cables which lie in water from 50 to 

 200 or 300 fathoms deep, have generally proved commercially 

 successful, whereas deep-sea cables, properly speaking, have not 

 done so. In fact, I may say, that at this moment there is not a 

 single deep-sea line which has proved permanently successful. 



Within a few weeks the great experiment of a second Atlantic 

 cable will be repeated, and, it is to be hoped, in the interest of 

 progress and science, as also for the sake of those who have 

 invested so largely in the undertaking, that it may be attended 

 with success. It may, indeed, be safely affirmed that the utmost 

 care has been bestowed upon the manufacture of this cable, and 

 that the chances of its success are infinitely greater than they were 

 on the last occasion, although there may be some reasonable 

 grounds for criticism, particularly as regards the mechanical 

 structure and durability of the outer sheathing. The short space 

 of an hour would not nearly suffice to treat this subject in any- 

 thing like an exhaustive manner, but I shall, at any rate, endeavour 

 to point out the principal points of interest involved in the con- 

 struction and treatment of deep-sea cables. 



First let me allude to the conductor. This consists generally 

 of a strand of three or seven copper wires, which are twisted 

 together so as to form a metallic rope. Deep-sea cables contain 

 generally only one conductor, as this is sufficient for the purpose 

 of establishing a communication ; but multiple deep-sea cables 

 have also been laid with temporary success. The conductor of a 

 submarine cable is the medium of the transmission of the electric 

 current ; it also acts as the internal lining of a Leyden arrange- 

 ment of great length, in which the gutta-percha or other insulat- 

 ing material employed acts the part of the glass jar, and the 

 sheathing of the cable the part of the external tinfoil covering. 

 Considering the extraordinary aggregate surface of long submarine 



