24 PETER GUTHRIE TAIT 



could be drawn from them. The outstanding difficulty was the uncertainty 

 that all possible sources of heating had been taken account of. After some 

 years of laborious experimenting the research was finally abandoned. 



When Nature was started in 1869 the Editor, (Sir) Norman Lockyer, 

 secured the services of Tait not only as a reviewer of books but also as a 

 contributor of articles ; and, especially during the seventies, Tait supplied 

 many valuable and at times very racy discussions of scientific developments. 



In 1871 as President of Section A at the Edinburgh meeting of the 

 British Association, Tait gave a characteristic address (Scientific Papers, 

 Vol. i, p. 164), in which Hamilton's Quaternions and Kelvin's Dissipation 

 of Energy are held up to admiration. 



The publication in 1873 of Tyndall's Forms of Water, in which the 

 work done by J. D. Forbes in the elucidation of Glacier motion was some- 

 what belittled, roused Tail's indignation and led to a controversy of some 

 bitterness (see Nature, Vol. vm, pp. 381, 399, 431). Tyndall defended 

 himself in the Contemporary Review ; and Tail's final reply, in which 

 Tyndall's quotalions from ihe writings of Forbes are shown to be so in- 

 complete as to lead the reader lo a false conclusion, appeared in the 

 English iranslalion of Rendu's Glaciers of Savoy ediled by Professor 

 George Forbes (Macmillan and Co., 1874). 



To Good Words of 1874 Tait contributed a series of most readable 

 articles on Cosmical Astronomy, which embodied his lectures delivered to 

 the Industrial Classes in the Museum of Science and Art, now known as the 

 Royal Scottish Museum. At the same time Balfour Stewart and he launched 

 their Unseen Universe upon an astonished world. 



Before 1880 the Editors of the new edition of the Encyclopaedia 

 Britannica secured Tait as the contributor of the articles Hamilton, Light, 

 Mechanics, Quaternions, and Radiation. The two longest articles namely 

 Light and Mechanics were afterwards published, with additions, as separate 

 books ; while the article on Radiation is practically embodied in his book 

 on Heat. 



While all this literary work was going on, he was studying the errors 

 of the Challenger Thermometers, writing an elegant paper on Mirage, 

 investigating the intricacies of knots, pushing on his quaternion investigations 

 when leisure permitted and putting together his Properties of Matter (1885). 



Throughout these years he also took a very practical interest in actuarial 

 mathematics. A great believer in the benefits of Life Assurance he was 



