LIFE AND WORK OF LORD KELVIN THOMPSON. 757 



Fourier's equations), which he later embodied in the curb signal 

 transmitter, namely, that the coefficient of the simple harmonic term 

 in the expression for the electrical potential shall vanish. In Decem- 

 ber, 185G, he described to the Royal Society his plan for receiving 

 messages, namely, a sort of Helmholtz tangent galvanometer, with 

 copper damper to the suspended needle, the deflections being observed 

 by watching through a reading telescope the image of a scale re- 

 flected from the polished side of the magnet or from a small mirror 

 carried by it. As we all know, he abandoned this subjective method 

 for the objective plan in which a spot of light from a lamp is 

 reflected by the mirror upon a scale. There is a pretty story — which 

 is believed to be true — that the idea of thus using the mirror arose 

 from noticing the reflection of light from the monocle which, being 

 short-sighted, he wore hung around his neck with a ribbon. 



The story of the Atlantic cable, of the failure of 1857, of the brief 

 success of 1858, has so often been told that it need not be emphasized 

 here. Thomson, after the failure of the first attempt, was called 

 upon to take a more active part. He had discovered to his surprise 

 that the conductivity of copper was greatly affected — to an extent 

 of 30 or 40 per cent — by its purity. So he organized a system of 

 testing conductivity at the factory where the additional lengths were 

 being made, and was put in charge of the test room on board the 

 Agamemnon in 1858. "N^Hiitehouse was unable to join the expedition, 

 and Thomson, at the request of the directors, undertook the post of 

 electrician in charge, without any recompense, though the tax on his 

 time and energies was very great. 



Sir Charles Bright has given us the following little silhouette of 

 Thomson : 



As for the professor * * *, he was a thorough good comrade, good all 

 round, and would have taken his "turn at the wheel" (of the paying-out 

 brake) if others had broken down. He was also a good partner at whist when 

 work wasn't on ; though sometimes, when momentarily immersed in cogibun- 

 dity of cogitation, by scientific abstraction, he would look up from his cards 

 and ask, " Wha played what?" 



After various disheartening mishaps success crowned their efforts. 

 Throughout the voyage Thomson's mirror galvanometer had been 

 used for the continuity tests and for signaling to shore, with a bat- 

 tery of 75 Daniell cells. The continuity was reported perfect, and the 

 insulation had improved on submersion. On August 5 the cable 

 was handed over to Mr. AMiitehouse and reported to be in perfect 

 condition. Whitehouse at once abandoned the Thomson mirror in- 

 struments and began working with his own i^atented apparatus using 

 heavy relays and a special transmitter with induction coils. He 

 sent in no report to the directors for a week, while he made ineffectual 



