1854.] 



OBSERVATIONS ON A TELEGRAPH LINE BETWEEN EUROPE AND A3IERICA. 



The transatlantic cable, if the machinery is multiplied, and 

 sixteen machines are employed, could, we have little doubt, 

 complete the cable in six or seven months. 



The third diiEculty is, " a ship big enoueh." This can be 

 no difficulty, for if one would not do, surely twenty would. 

 'What is the objection to sending it by trips or in pieces ? 

 Could it not be attached, as it was laid down, to a buoy ? A 

 vessel of 1000 tons could surely cari-y 400 tons of coil, for our 

 cable would not exceed 12,000 tons. 



Another important matter to be determined is, to what ex- 

 tent a galvanic current can be sent on an insulated wire. This 

 has also been determined, for in favourable states of the atmos- 

 phere, lines in this country have been so insulated as to work 

 in one circuit from 800 to 1000 miles. 



In my work on the Telegraph, p. 1.52, I there state that the 

 greatest distance that any of the lines had worked in one cir- 

 cuit, was from Boston to Montreal, via New*York, Buffalo, and 

 Toronto, a distance of about 1500 miles. This was done when 

 the earth was frozen, and the lines insulated by frost. 



The entire leng-th of the telegraph line from New York to 

 New Orleans, via Charleston, Savannah, and Mobile, is lOOG 

 miles, and even this distance has been worked as one circuit by 

 the aid of an instrument termed a connector, the effect of which 

 is to cause one circuit to work the other through the entire 

 series, thus producing a result similar to working through the 

 entire line in one circuit. 



As late as December 3, 1853, despatches were written direct 

 through from New Orleans to Philadelphia and New York, on 

 the National Telegraph line, the weather being cold and the 

 earth frozen. In doing so, the only connector or repeater used 

 was an insulated screw on the back of the register, invented by 

 a distinguished telegraphic engineer, W. C. McRea, of this city, 

 which ic now the simplest mode employed ; but this distance 

 would require at least 30 Grove's cups, of a pint each, for every 

 100 miles, making about 480 cups, or 240 each side. I think 

 this number of the battery of iMr. C. T. Chester would be 

 amply sufficient. If a copper and zinc battery were emploj'ed, 

 the number would have to be increased to about 30 to 40 cups 

 every 100 miles, but even with this large batteiy, the expenses 

 would be less than with the Grove's battery. In preparing the 

 batteries, it is even po.ssible to determine mathematically be- 

 forehand the amount of resistance and the force necessary to 

 overcome it ; and thus to proportion the number and size of 

 the plates to the distance to which the wires extend. Large 

 wires are better conductors than small ones. Copper is a much 

 better conductor than iron; and as a thinner wire answers the 

 purpose of conduction, it may bo much more easily insulated. 



The several conditions may all be calculated from the beau- 

 tiful formula of Ohm. 



In some recent experiments of Professor Faradaj-, that dis- 

 tinguished philosopher, by some of the results he obtained, has 

 thrown much light upon the action of voltaic electricitj' in the 

 submerged wire of the electric telegraph. 



He first determines by actual experiment, that when copper 

 Tyire is perfectly covered with gutta pcrcha, so high is tlie insu- 

 lation that in 100 miles of such wire, when fully charged by an 

 intensity battery of 350 pairs of plates and submerged in water, 

 the dcllexion of a delicat3 galvanometer was not more than 5 

 degrees. The great perfection in the covering of the wire may 

 be judged of bv this fact alone. The 100 miles of wire Wiis 1- 



16th of an inch in diameter ; the covered wire wa.s 4-16ths ; 

 the gutta percha on the metal was 0"1 of an inch in thick- 

 ness. There could not be a better proof than this, that gutta 

 pcrcha is one of the best insulating agents we have, which iiict 

 I have before stated in my work on the Tclegniph. He expe- 

 perimented with the subterraneous wires which exist between 

 London and Manchester, and when they were all connected to- 

 gether so as to make one series, they made almost the distance 

 as determined by Lieutenants Ben-j-man and Mauiy between 

 the Irish coast and Newfoundland, being 1500 miles, and hav- 

 ing introduced galvanometers at intervals of about 400 miles, 

 he found that when the whole 1500 miles were included, it re- 

 quired tii:o nf.rondM for the electric stream to roach the last 

 instrument, which was placed at the end. In this instance the 

 insulation was not as perfect, still the result shows that it will 

 rcfjuire a little over two seconds to cross the Atlantic by tele- 

 graph, which is about the rate of 750 miles in a second, which 

 result is far below those obtained by the London and Brussels 

 telegraph, which is stated at oidy 2700 miles in a second, even 

 with a copper wire, while it will be remembered that Wheat- 

 stone, in 1834, with copper wire, made the velocity of the 

 electric cun'ent 288,000 miles per second — a considerable dif- 

 ference. 



The whole of this dificrence, according to Professor Faraday, 

 depends upon the lateral induction of the wire carrj-ing the 

 current. " The production of a polarized state of the particles 

 of neighbouring matters by a excited body, constitutes induc- 

 tion, and this arises from its action upon the particles in imme- 

 diate contact with it, which again act upon those contiguous to 

 them, and thus the forces are transferred to a distance. If the 

 induction remain undiminished, then perfect insidation is the 

 consequence; and the higher the polarized condition which 

 the particles can acquire or maintain, the higher is the inten- 

 sity which may be given to the acting forces. In a word, in- 

 sulators may be said to be bodies whose particles can retain the 

 the polarized state ; whilst conductors are those whose particles 

 cannot be permanently polarized." And in regard to long cir- 

 cuits, such as those described, their conducting power cannot 

 be understood, whilst no reference is made to their lateral .static 

 induction or to the conditions of inten.sity and ipiautity which 

 then comes into play. 



The conducting power of the air and water wires are alike 

 for a constant current. This, according to Faraday, is in per- 

 fect accordance with the principles and with the definite cha- 

 racter of the electric force, whether in the static, or current, or 

 transition st;tte. AVhcn a voltaic current ol'a certain intensity 

 is sent into a long water wire, connected at the further extre- 

 mity with the earth, part of the force is in the first instance oc- 

 cupied in raising a lateral induction round the wire, ultimately 

 equal in intensity at the near end to the intensity of llw liattory 

 stream, and decreasing gradually to the earth end. 



In the report of Professor Farada}', which is given in the 

 JmiiiIou P]iilo.ioplunil Alac/aziiif for JIurch, he there, in con- 

 clusion, refers to the terms intensili/ anil ijiioiilili/. These 

 terms, he remarks, or ct|uivalents for thcni, cannot be dispensed 

 with by those who study both the static and dyuamic relations 

 of electricity. Every cun'cnt where there is resistance, has the 

 .static element and induction involved in if, whilst every case 

 of insulation has more or less of the dynamic element nml con- 

 duction ; and we have .seen that the .>iame voltaic .source, flie 

 same current in the same length of the sjune wire givci a dil- 

 fercnt result, as the intensity is made to varv with variations of 



