388 THE PHYSICAL GEOGBAPHY OF THE SEA. 



a wire could be laid in tlie Black Sea, one conid be laid in tlie 

 deep sea as well, for tliere is reason to believe tliat tlie currents of 

 tlie ocean do not extend beyond a few hundred fathoms in its 

 depths. 



There seems to be a sort of general impression that the amount 

 of slack cable required to feed the currents of the sea is ver j con- 

 siderable. A little reflection will show that this is not the case, 

 especially along the telegraphic plateau. 



The current which requires the greatest proportion of slack is 

 one which sweeps across the cable at right angles ; whereas the 

 great circle along which the Atlantic Cable was laid crosses the 

 Gulf Stream so obliquely that a vessel running along from 'New- 

 foundland to Ireland may be considered as running with that 

 stream for much of the way. 



The current along the telegraphic plateau seldom exceeds two 

 knots an hour ; it rarely amounts to that. But, to present the 

 strongest case against the view I am advocating, let us suppose 

 that the current runs all the way across at the rate of two knots, 

 and at right angles to the cable, and that a vessel with the proper 

 length of the Kogers cord on board were to set off, to "pay and 

 go" with it from Newfoundland to Ireland. The cord, being paid 

 over with 10 per cent, of slack, is heavy enough to sink at the 

 rate of two miles an hour ; the current, let it be supposed, de- 

 scends to the maximum depth of half a mile ; any given part of 

 the cord, therefore, as it goes out and sinks at the rate of two 

 miles an hour, occupies fifteen minutes in sinking the first half 

 mile. During these fifteen minutes only it is exposed to the cur- 

 rent, by which it is swept half a mile to the right or left of the 

 track of the ship ; then reaching the still water below, it settles 

 down through it until it reaches bottom. 



Thus, in the case supposed, the cord would not lie in a zigzag, 

 but more in a straight line all the way across, and only half a 

 mile to the right or left of the path actually made by the keel of 

 the ship. The difference in distance by such a path and such a 

 line would be practically inappreciable, and yet the case supposed 

 is an exaggeration of the case that is actually presented. For a 

 part, if not for the whole distance, there is an under current which 

 would bring the cable back toward the wake of the ship, thus tend- 

 ing to counteract the effect of the uj)per current in sweeping it off. 



