NATURAL PHILOSOPHY. 127 



THE ATLANTIC TELEGKAPH. 



Two schemes are now before the public for reviving this important 

 enterprise : the one for a continuous cable from Ireland to Newfound- 

 land, the other for a line in four sections, the points of intermission 

 being the Faroe Islands, Iceland, Greenland, and Labrador. The pro- 

 moters of each of these enterprises appear most confident, not only of 

 the perfect feasibility of their own plan, but also of the existence of fatal 

 defects in that which is propounded by their rivals. On behalf of the 

 sectional undertaking, for example, it is urged that the difficulty of 

 working through long circuits, owing to the retarding influence of 

 inductive electricity, increases in about the square of the length of 

 the line when long insulated wires are laid down either in the earth 

 or under water. If this were absolutely true the delay arising from 

 reading off and re-transmitting messages at four stations would still 

 have to be weighed against that springing from the cause as- 

 signed. But it appears by no means certain that the theory thus 

 broadly laid down is to be unhesitatingly accepted as the embodiment 

 of an unvarying law. The most competent electricians aver, that the 

 operation of the law referred to is susceptible of considerable modifi- 

 cation from surrounding circumstances. It has been found, that 

 whereas the induction increases only as the circumference of the cop- 

 per wire, its conducting power increases as the square of its diameter ; 

 and hence it is inferred that if a wire of considerable size be coated 

 with insulating material to such a thickness as shall give the same in- 

 duction as to a smaller wire, an enormous augmentation of speed will 

 be attained. Taking these conclusions as a basis of calculation, it is 

 estimated that such a cable as that which is now being manufactured 

 to connect Ireland with Newfoundland, containing 510 pounds of cop- 

 per and 550 pounds of gutta-percha to the mile, will transmit from 

 eight to twelve words per minute. If this be so, such rapidity is as 

 great as we can reasonably hope to attain. 



On the other hand, it is alleged that if two lines of the same 

 dimensions and cost as regards copper and insulation were laid, 

 one for 500 miles and the other for 1,500, the former could be 

 worked through for messages at nearly nine times the speed of the 

 latter. According to this theory, the sectional cable to Labrador, by 

 way of Iceland and Greenland, would transmit 108 words per minute; 

 but this is obviously incredible, since it is known that the English land 

 lines are seldom worked at a higher speed than 22 words per minute. 



There are some arguments urged with regard to the rival lines 

 upon which every one gifted with common sense is competent to form 

 a judgment. Every one can understand that on the Labradof line 

 great additional expense must be entailed by the necessity of keeping 

 at each intermediate station a staff of clerks to read off the messages 

 and retransmit them along the next section. It needs no profound 

 scientific training to comprehend that the inaccessibility of the coasts 

 of Iceland and Greenland,' save during six weeks of the year, must 

 throw great difficulties in the way of repairing some portions of the 

 cable if they should chance to get out of working order. 



An average store of worldly experience and geographical acquire- 

 ment will enable any one to realize the difficulty of keeping in good 



