NATURAL PHILOSOPHY. 117 



away, it cannot tell why. What is the matter with it? Where is the pain? 

 What part is hurt? Answer, there is none. In a small room on the Irish 

 coast a bit of copper wire is fixed on the table or the wall, and knowing men 

 are coaxing it to tell them what has happened a thousand miles off in the mid 

 abyss of the ocean. Its vitality expires, its pulsation grows weaker; it 

 responds more and more feebly to the tortures of science, and the very means 

 used to rouse it from its stupor, draw on its constitution. In their urgency, 

 the operators cut off their own hopes, and it is now suspected that they have 

 done themselves no small part of the mischief that they deplore. What is 

 this but the old story of the genius, maliciously true, keeping the very letter 

 of his bond, doing superhuman service, but gone forever if a word or a 

 movement be omitted ? There is too much reason to fear that the affair is 

 reduced to a post mortem examination. There is a length of wire, but how 

 long no man can say. It is, indeed, almost the greatest wonder of the aire, 

 and, fairly considered, beats even the Atlantic Telegraph itself, should that 

 ever be an existent fact, that our men of science can stand at one end of a 

 fine copper wire and ask it how long it is. " Answer, wire, are you 10 

 miles long, or 270, or 560, or 1,000, or even 2,000? What is the nature of 

 your fracture or injury? " Witchcraft itself cannot beat such divination. It 

 is even some comfort to reflect, that, though for the present science docs us 

 no good, yet it gains by our failure, and though we do not yet obtain what 

 we want, we know more. 



Since the deposition of the cable, says the London News, a great variety of 

 interesting experiments have been performed to show the kind of electricity 

 best suited for working through the line, both in a perfect and imperfect con- 

 dition ; and the results which have been arrived at are both useful and inter- 

 esting. The high tension electricity from the induced coils was found to 

 bum up and destroy a wire where a fault in the gutta-percha w r as made. The 

 second experiment was made with discharges from Henley's magneto-elec- 

 tric machine. This was found to suffer a slight loss through the fault, but 

 not to injure the wire at the point of egress in any way as long as negative 

 discharges only were sent through. The direct battery current, of great 

 quantity, but low tension electricity, was found to answer best, and to cause 

 less injury to the cable, and to suffer less loss through the fault; but some 

 copious currents of this low tension electricity are now unable to make the 

 cable show signs of activity even with the most delicate arrangement of Pro- 

 fessor Thomson's reflecting galvanometer. Much has been said about this 

 beautifully sensitive little instrument, yet but few know its nature or the advan- 

 tages it possesses over other galvanometers in observing very minute currents 

 of electricity. It consists of a coil of very fine insulated wire, in the interior 

 of which is suspended a very small mirror of the finest microscopic glass, to 

 the back of which are fastened two magnetic needles not more than a quar- 

 ter of an inch in length. The two needles, with the reflecting mirror they 

 bear, not weighing more than two grains, are suspended by a single fibre of 

 silk. When the instrument is in use a ray of light is thrown upon the mir- 

 ror, and is reflected upon an index board. The very faintest currents of elec- 

 tricity are measured by these means ; for the very faintest deflection of the 

 needles, caused by an almost imperceptible current of electricity passing 

 through the coil, of course, is very perceptible upon the index board by the 

 motion of the reflected spot of light. 



The supposed difficulty of working through the cable, after it was sub- 

 merged, which was so much talked about, has turned out to be altogether a 



