THE ATLANTIC TELEGRAPH. 335 



Bearing in mind the quiet wliicli reigns at tlie bottom of tlie 

 deep sea ; tliat the bed of the ocean is protected from the abrading 

 action of its currents by a cushion of still water ; that there is no 

 running water down there ; and that the jDressure is such as to ob- 

 struct, if not forever to prevent, the decomposition of all animal 

 and vegetable matter when once lodged there, let us inquire a lit- 

 tle more minutely as to the use of that iron wrapping for the deep- 

 sea cable. 



It was not to protect the cable from abrasion after it was lodged 

 on the bottom, for we have discovered that there are no abrading 

 forces there to fret it. 



It could not have been to keep the cable down, for we have seen 

 that the lightest dregs that float in the water are, when allowed to 

 settle on the bottom of the deep sea, heavy enough and stout 

 enough to remain there. 



It could not have been on the score of economy, for the cost of 

 the cable must have been nearly, if not quite doubled on account 

 of the iron wrapping. 



The wrapping of iron wire without does not, I imagine, tend to 

 improve the conducting powers of the copper wire within ; and — 

 besides the cost and the dif&culty of manipulation, owing to in- 

 crease of both size and weight which this iron wrapping gives the 

 cable — that increased size and weight had something to do with 

 the electrical difiiculties of the cable. What the real nature of 

 these difiS.culties is must be matter of conjecture, but the conject- 

 ure which seems to me most plausible is one of this sort : the con- 

 ducting wire is a strand of seven copper threads twisted together; 

 this strand is then coated with gutta-percha, making a straight 

 cord about the size of a lady's finger ; this cord is then served with 

 eighteen strands of iron wire, consisting of seven threads each, 

 wrapped spirally about it. Now, in the process of paying out in 

 the deep sea, and in holding back, the strain of the two or three 

 thousand pounds which was brought to bear upon the cable, in 

 order to prevent it from running out too fast, was first borne prin- 

 cipally by the straight cord, consisting of gutta-percha and the 

 conducting wires, rather than by the spirally -laid iron wires. 



To illustrate this proposition, namely, that the strain was brought 

 to bear upon the straight centre-piece or heart, as the conducting 

 wire and its coating of gutta-percha may be called, rather than 



