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THOMSON.

THOMSON, SirWilliam,F.R.S., LL.D., D.C.L., was born at Belfast in June, 1821. His father, the late Jameb Thomson, LL.D., was lecturer on mathematics at the Royal Acade- mical Institute in Belfast, but on hia appointment to the professor- ship of that science in the Univer- sity of Glasgow, he removed thither with his family. At the early age of eleven William entered the Col- lege, and shortly after completing his course at Glasgow he removed to Peterhouse, Cambridge, where ho graduated in 1815 as second wrangler, being immediately after- wards elected to a fellowship. In 18kJ he was made Professor of Natural Philosophy in the Uni- versity of Glasgow, and still occupies that post. In the same year ho accepted the editorship of the Cambridge and Dublin Mathematical Journal. To this magazine, which he continued to edit for about seven years, he contributed valuable ad- ditions to the mathematical theory of electricity, and among the prin- cipal of these was his pai)er on the ** Distribution of Electricity on Spherical Conductors," published in 1818. In 1855 Mr. Thomson de- livered the Bakerian Lecture. It was entitled, " Electrodynamic Pro- perties of Metals," and contained a series of experimental investiga- tions of the highest value. Among the most important of his contri- butions to the advancement of elec- trical science are the construction of several beautiful instruments, and their application to the study of atmospheric electricity. His quadrant and portable electrome- ters, owing to their diversities of application and extreme delicacy and accuracy, have been of the greatest service; a modification of the former has been very success- fully used at the Kew Observatory, to indicate and self -register changes in the electric state of the atmo- sphere. But it is in connection with submarine telegraphy that Mr. Thomson's labours in electrical

science are best known, he being the inventor of the Mirror Galva- nometer and the Siphon-Recorder, which, owing to their extreme de- licacy, can be worked by very low battery power, a circumstance that tends greatly to the preservation of the cables. To the science of mag- netism also Sir W. Thomson has made important additions, but it is in the investigation of the nature of heat that his extraordinary power of mathematical insight is seen to the greatest advantage. Owing to their abstruse nature, it is im- possible to give in this work a detailed accoimt of the results of his experiments, but the following may be mentioned as the princi- pal : — The conversion of water at the freezing point into ice without expenditure of force ; the specific heat of substances ; the heating of indiarubber by sudden stretehing ; the relation between the force ex- pended and the heat produced in the compression of a gas ; and iiie universal tendency in nature to the dissipation of mechanical energy. The last of these is in many re- spects one of the most extraordinary generalizations of modern science- Sir William Thomson's views on the subject were published in 1852 in the Philosophical Magaxine. The limits of this notice do not allow any reference to many other peters by this distinguished worker in science: we can only mention those on " Thermal Effecte of Fluids in Motion ;" the " Mathematical Theory of Elasticity;*' the " Rigidity of the Earth;" the "Determina- tion of a Ship's Place at Sea from Observation of Altitudes ;" and on "Approach caused by Vibration." On the successful completion of the Atlantic Cable in 1866 he received the honour of knighthood, and was presented with the freedom of the city of Glasgow. For his profound and extensive attainments Sir Wil- liam has received many acknow- ledgments. The degree of LL.D. was conferred on him successiTely