WILLIAM THOMSON, LORD KELVIN. 897 



SO called Kerr effect, which on Thomson's suggestion was sought for 

 unsuccessfully by Faraday was not actually discovered till 1876. 



In 1846 Thomson, then only 22, was appointed to the Chair of 

 Natural Philosophy in the University of Glasgow. This position he 

 held for fifty years. There now began a most active period of his 

 life and many of his students afterward became noted in physical 

 science. 



Thomson's studies covered the widest range including Kinematics 

 and Thermodynamics. Important discoveries, such as the Thomson 

 thermoelectric effect were made, and inventions of the greatest scien- 

 tific and technical value worked out. Among these latter may be 

 mentioned the famous mirror galvanometer, of exceeding sensibility 

 and almost essential to ocean telegraphy. There was also the well 

 known water dropper leading to the so called Mouse Mill Replenisher. 

 His great invention of the siphon recorder for cable telegraphy was 

 made in 1869, and later his improved deep sea sounding apparatus 

 and his mariner's compass improvements, aided greatly the art of 

 navigation, in which he had always possessed a keen interest. The 

 briefest record of his great activity in various fields is permissible here. 



In 1851, elected to the Royal Society, his papers on Thermo- 

 dynamics brought him into contact with Helmholtz, Joule and later 

 Clerk Maxwell. It happened that a few years prior to 1858, Thomson 

 had made a study of the conditions of transmission of signals in long 

 submarine cables, using the Fourier mathematics to determine the 

 factors of retardation, etc. In 1858 the first Atlantic Cable was laid, 

 and for a time it was successful ; failing after several hundred messages 

 had been transmitted. Such success as there was must be attributed 

 to Thomson, and the failure was probably caused by faults of insula- 

 tion made worse by allowing the cable to be manipulated at high 

 voltages and under conditions directly at variance with Thomson's 

 ideas and disapproved by him. 



The great treatise by Thomson and Tait on Natural Philosophy 

 was projected about this time. Part I however was not published 

 until 1879 and Part II not until 1883. The authors thereafter 

 abandoned the publication of the originally contemplated two addi- 

 tional volumes. 



Following the London International Exhibition, Thomson took an 

 active part in the committee work in 1862 involving the establishment 

 of values and names for the international electrical units, such as the 

 ohm, the volt and the farad. This pioneer work has been continued 

 at the later international congresses and conferences, several of which 

 he attended. 



