The First Atlantic Cables 



proportions are presented as it touches the shore, 

 for a distance of one and three-quarter miles, 

 where type C has a diameter of two and one-half 

 inches. The weights of material used in this 

 cable are: copper wire, 495 tons; gutta-percha, 

 315 tons; jute yarn, 575 tons; steel wire, 3,000 

 tons; compound and tar, 1,075 tons; total, 

 5,460 tons. The telegraph-ship Faraday, spe- 

 cially designed for cable-laying, accomplished 

 the work without mishap. 



Electrical science owes much to the Atlantic 

 cables, in particular to the first of them. At 

 the very beginning it banished the idea that 

 electricity as it passes through metallic conduc- 

 tors has anything like its velocity through free 

 space. It was soon found, as Professor Menden- 

 hall says, "that it is no more correct to assign 

 a definite velocity to electricity than to a river. 

 As the rate of flow of a river is determined by the 

 character of its bed, its gradient, and other cir- 

 cumstances, so the velocity of an electric current 

 is found to depend on the conditions under which 

 the flow takes place. "* Mile for mile the origi- 

 nal Atlantic cable had twenty times the retard- 

 ing effect of a good aerial line; the best recent 

 cables reduce this figure by nearly one-half. 



In an extreme form this slowing down reminds 

 us of the obstruction of light as it enters the at- 

 mosphere of the earth, of the further impedi- 

 ment which the rays encounter if they pass from 



* "A Century of Electricity." Boston, Houghton, 

 Mifflin & Co., 1887. 



49 



