SUBMARINE TELEGRAPHY 215 



first cable out of the water weighed little more than half as much 

 as the new cables ; in water, it weighed more than they do. Its 

 strength was 80 cwt., and the maximum strain during its sub- 

 mersion was nearly one ton ; the ordinary strains varied from 

 1,500 to 1,900 ibs. 



From these figures we may learn the progress which has 

 been made in the mechanical construction of the cables, and the 

 diminished risk which attends their submersion. 



The history of the several attempts to lay the cables helps 

 to show the progress made in the construction, and bears out 

 the conclusions as to the improvements effected. In August 

 1857 a first attempt was made to lay an Atlantic Cable ; 330 

 knots were laid, starting from Valentia. Then the cable broke, 

 the indicated strain being about 27 cwt. The retarding friction 

 on this occasion was produced by two blocks of wood which were 

 clamped round a small drum. Before the next attempt the 

 Appold brake had been invented, and with the sanction of Mr. 

 Penn, Mr. Field, Messrs. Easton and Amos, Mr. Lloyd, Mr. 

 Everett, and Sir C. Bright, it was applied to the paying-out 

 machinery. This brake is an excellent contrivance, by which 

 the required strain is readily produced and maintained unal- 

 tered ; the retarding friction being quite independent of the 

 condition of the rubbing surfaces. This brake was successful, 

 and has been used ever since. The 1858 expedition began opera- 

 tions on June 26 by a splice in the middle of the Atlantic, join- 

 ing the cables contained in the ' Niagara ' and ' Agamemnon.' 

 The cable fouled the ' Niagara ' and broke. A second splice was 

 at once made, and successfully lowered to the bottom. When 

 the ' Agamemnon' had paid out 37^ miles, and the ' Niagara* 

 43 miles, the electrical tests showed that the copper conductor 

 of the cable was severed. In technical language, there was a 

 loss of continuity. The ' Niagara ' endeavoured to haul in the 

 cable, which shortly broke for the third time. On June 28 

 another splice was made ; but after 111 miles had been paid out 

 the cable broke for the fourth time, with a strain indicated of 

 2,200 Ibs., or nearly one ton. On July 28 another splice was 

 made, and this time the cable did not break, but was laid 

 successfully as a mechanical operation, but unsuccessfully in all 

 other senses. As before stated, a want of continuity did occur. 



