LIFE AND WORK OF LORD KELVIN THOMPSON. 761 



hypothesis was adequate to explain all the properties of matter, the 

 conception remains to all time a witness to his extraordinary powers 

 of mind. 



In 1870 Lady Thomson, whose health had been failing for several 

 years, died. In the same year the University of Glasgow was re- 

 moved from the site it had occupied for over four centuries to the 

 new and splendid buildings on Gilmore Hill, overlooking the Kelvin 

 River. Sir William Thomson had a house here in the terrace as- 

 signed for the residences of the professors, adjoining his laboratory 

 and lecture room. From his youth he had been fond of the sea, and 

 had early owned boats of his own on the Clyde. For many years his 

 sailing yacht, the Lalla Rookh^ was conspicuous, and he was an ac- 

 complished navigator. His experiences in cable laying had taught 

 him much, and in return he was now to teach science in navigation. 

 First he reformed the mariner's compass, lightening the moving parts 

 to avoid protracted oscillations and to facilitate the correction of the 

 quadrantal and other errors arising from the magnetism of the ship's 

 hull. At first the Admiralty would have none of it. But the com- 

 pass is now all but universally adopted both in the navy and in the 

 mercantile marine. 



Dissatisfied with the clumsy appliances used in sounding, when 

 the ship had to be stopped before the sounding line could be let down, 

 he devised the now well-known apparatus for taking flying sound- 

 ings by using a line of steel piano wire. He had great faith in navi- 

 gating by use of sounding line, and once told me — apropos of a recent 

 wreck near the Lizard^ which he declared would have been impossible 

 had soundings been regularly taken — how in a time of a continuous 

 fog he brought his yacht all the way across the Bay of Biscay into 

 the Solent, trusting to soundings only. He also published a set of 

 tables for facilitating the use of Sumner's method at sea. He was 

 vastly interested in the question of the tides, not merely as a sailor, 

 but because of the interest attending their mathematical treatment 

 in connection with the problems of the rotation of spheroids, the 

 harmonic analysis of their complicated periods by Fourier's methods, 

 and their relation to hydrodynamic problems generally. He invented 

 the tide-predicting machine, which will predict for any given port 

 the rise and fall of the tides, which it gives in the form of a con- 

 tinuous curve recorded on paper, the entire curves for a Avhole 3^ear 

 being inscribed by the machine automatically in about four hours. 

 Further than this, adopting a beautiful mechanical integrator, the 

 device of his ingenious brother, Prof. James Thomson, he invented a 

 harmonic analyzer — the first of its kind — capable not only of solving 

 differential equations of any order, but of analyzing any given 

 periodic curve and exhibiting the values of the coefficients of tlie 



