152 ANNUAL OF SCIENTIFIC DISCOVERY. 



carrying half the line. They will then separate, and continue to lay out the 

 cable until they shall have reached their respective destinations. The wires 

 will enable them during the entire process to telegraph each to the other at 

 will, so that their combined movements will be, as it were, at the direction of one 

 mind. Hitherto, almost all the cables which have been lost have been sacrificed 

 from being placed in sailing vessels towed by steamboats. These have become 

 unmanageable in bad weather, and, to save themselves, have been obliged to 

 throw the coil overboard. This could not occur, if the countries most interested, 

 England and the United States, were to contribute first-rate steam men-of-war. 

 At all events, it is well to think, that in this instance, as there will be two ves- 

 sels, the line can scarcely be lost, for, even if one were obliged to sacrifice her 

 freight, the other could wind it up from the deep. The number of wires to be 

 used is not determined upon, and here again modern science has achieved a 

 great triumph. Of course, in a line of such length the amount of copper used 

 in the wire becomes an object of the gravest consideration in determining its 

 expense. Now, in telegraphs above ground, it has been found that the faci- 

 lity of transmitting a current has increased with the enlarged size of the wire. 

 The electricity has, as it were, a broader path to move on. Thus an imperfect 

 conductor can compensate for its defective state of conduction, by increase of 

 volume. Take, for instance, the two metals, copper and iron. Iron offers 

 seven times the resistance of copper to the passage of an electric current, but 

 by proportionally increasing the size of the iron wire, electricity will be as 

 readily transmitted through it as through the better conducting metal ; and 

 consequently iron wires, one-sixth of an inch in diameter, are used in the tele- 

 graphs of this country. It was dreaded, from such a course of reasoning, that 

 so enormous a line should not only be of the best conducting material, but 

 that it should also be of great thickness, which would vastly enhance the 

 expense, but Dr. Whitehouse has, in a series of over 4,000 experiments, 

 demonstrated that not the same, but rather an opposite condition operates in 

 submarine lines. It is to be remarked that the wires here are thoroughly isolat- 

 ed. so that the charge sent into one resembles the charging of a Leyden jar, 

 and, consequently, the smaller, within certain limits, the wire which is to be 

 charged, the more effective the operation of the electricity will be. This is a 

 result of the most important character, for otherwise the company would have 

 been put to enormous cost in employing larger wires, which would, in fact, 

 have been only operative to retard the telegraphic action." 



" So far. indeed, as regards the wire connection between the two countries, 

 there seems no doubt that it can be made; but that mechanical difficulty over- 

 come, there will remain the question whether telegraphic signals can be trans- 

 mitted through a submerged wire, of that length, however carefully it may be in- 

 sulated. On this point electricians and mathematicians are at variance. It is not 

 a simple question whether an electric current can be transmitted, but whether 

 the wire can be discharged, after transmission, quickly enough for the repetition 

 of telegraphic signals. 



" This difficulty first presented itself in the telegraph from Harwich to the 

 Hague. It was found that the water surrounding the wires prevented them 

 transmitting distinctive signals, the action of each one being prolonged so as to 



