KELVIN IN THE SIXTIES 267 



word; but in the syllable "toe" the "e" is as indistinct as the hur- 

 riedly written scrawl that you are very glad to get some one else to 

 read for you. 



Thomson wanted a receiving instrument which, unlike the ordinary 

 telegraph instruments used in post-offices and railway stations, could 

 render the interpretation of such suggestions possible in the hands of 

 an expert signaler, and he devised the mirror galvanometer speaking 

 instrument to obtain this result. 



Another most important fact that his theoretical investigation 

 brought out was that no increase of battery power could counteract the 

 retardation in the signals produced by an impurity existing in the 

 copper conductor of a cable, and hence that every yard of copper wire 

 used in the thousands of miles of a long cable must be electrically 

 tested for resistance before being used. 



But all this appeared to the electrician as arising from the igno- 

 rance of an inexperienced young man who had never erected a mile of 

 telegraph line in his life, and would not have been given a job in any 

 telegraph office. And so when signals through the 1858 Atlantic cable 

 became weak, and a message from the president to our queen took 

 thirty hours in transmission, although containing only 150 words, and 

 which would need only three or four minutes to transmit through any 

 one of the good Atlantic cables of to-day, the only remedy of those who 

 looked down on the theories of the young Glasgow professor was to use 

 Whitehouse's " thunder pump," a magneto-electric machine which pro- 

 duced a sudden large electromotive force when the armature of the 

 permanent magnet was jerked off the poles of the magnet. But these 

 shocks only sent sparks through the gutta-percha insulating coating 

 and hurried the poor cable to its doom, so that even the three words 

 per minute which would have been the utmost limit of speed possible 

 had this cable been entirely uninjured, were replaced by absolute 

 silence. 



But Thomson energetically struggled on and, pursuing (as he told 

 me afterwards) a " Parnell-Biggar policy " at the board meetings of 

 the Atlantic Cable Company, obstructed all business until the directors 

 promised to have all the copper wire tested for resistance before being 

 made into cable; and thanks to Thomson for his theory of signaling, 

 to that engineer of energy and surprising resource, even when quite a 

 lad, Sir Charles Bright, to Captain Anderson of the Great Eastern, 

 and to all those who have followed in the history of submarine cable 

 development the London Stock Exchange is by cable to-day within 

 thirty seconds of Wall Street. 



Thomson's work in connection with submarine telegraphy has been 

 epoch-making. But thirty-three years ago it was associated with what 

 I felt was a national loss. I give it in an extract from a long letter 



