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successfully till just before the evacuation of the Crimea by the 

 Alli.-s. 



It would be tedious to notice the various successful and un- 

 siiivrssful attempts which have been made since the year 1837 to 

 establish submarine cables, suffice it to state the general results of 

 the experience obtained, which goes to prove that the difficulty of 

 tbmerging and working submarine cables is small in shallow and 

 narrow waters, but increases in rapid ratio with the depth and 

 breadth of the ocean to be traversed. 



An inquiry into this most interesting subject may be divided 

 into tliree sufficiently distinct heads, namely, the mechanical 

 problem of constructing and submerging the cable ; the electrical 

 condition of the submerged cable ; and, lastly, the question of 

 suitable instruments. 



The mechanical problem has been discussed lately at great 

 length at the Institution of Civil Engineers, I therefore propose 

 to limit myself to a recital of the principal points of interest which 

 may be considered as established both by theory and in practice. 



The cable should be of small specific weight and of great 

 tensile strength, in order that its descent through the water may 

 be retarded by the resisting medium to such a degree that the 

 velocity of maximum acceleration may not exceed one-fourth, or at 

 most one-third, of the velocity of the vessel. This condition of a 

 " balanced cable " being fulfilled, there remains the tendency of 

 the cable to slide down the inclined trough of the water, and it 

 has been proved that this force equals, under all circumstances, 

 the weight of a length of cable (less the weight of water it dis- 

 places), reaching from the vessel perpendicularly to the bottom of 

 the sea. The same amount of retarding force must at least be 

 applied to the paying-out brake to prevent great waste of cable, 

 and the cable itself must of course be sufficiently strong to bear 

 this strain without injury to the insulated wire or wires. 



Messrs. Longridge and Brooks have been the first to prove, 

 I believe, that currents in the ocean cannot sensibly augment the 

 strain upon a descending cable, nor are they likely to occasion 

 considerable loss. 



It has been proposed to increase the floating power of deep-sea 

 cables, by attaching floats at intervals ; but it appears to me that 

 such appliances, which depend upon the unerring dexterity of 



