SCIENCE IN THE INDUSTRIAL WORLD 



overcame the possibility of a repetition of the accidental 

 breaking of the cable by the paying-out machinery. 

 Another great invention, made by the moving scientific 

 spirit of the enterprise, Professor Thomson (afterward 

 Lord Kelvin), was that of his mirror-speaking instrument, 

 or "marine galvanometer," which eventually revolu- 

 tionized long-distance electric signaling and testing on 

 shipboard. This instrument consisted of a tiny magnet 

 and a reflector, weighing together about a grain, with 

 which transmitted messages were magnified by reflected 

 light, so that the faintest current could be detected and 

 signals interpreted. 



Early in 1858, the new cable being completed, a second 

 attempt was made. This time, however, a new plan was 

 adopted, and instead of beginning the cable-laying 

 from one end, both ships, the same Agamemnon and 

 Niagara as before, proceeded to a point in mid-ocean, 

 spliced the two ends of the cable together, and headed 

 in opposite directions paying out the cable as they went. 

 When three miles apart the cable broke by becoming en- 

 tangled in the machinery of the Niagara. Both ships 

 at once put about, a new splice was made, and again 

 they headed for opposite shores. All went well for a 

 few hours when the cable again parted this time ap- 

 parently somewhere at the bottom of the ocean. Again 

 both boats put about, returned to the rendezvous, and 

 spliced the cable for a third time. 



This time things looked more hopeful, and mile after 

 mile of cable was laid, everything moving smoothly. 

 Something over a hundred miles had been reeled off by 

 each ship a total of two hundred and twenty-three 



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