July 25, 1901] 



NA TUKE 



j'-'o 



additional cooling below -205^ C. which it had gained 

 by expansion. Thus the high-pressure gas which suc- 

 ceeds it reaches the expansion-valve at -215 C, and 

 expanding from a lower temperature gains by free expan- 

 sion a greater amount of cooling, say 15", so that it now 

 passes away over the coil at - 230' C. and cools to this 

 temperature the compressed gas by which it is succeeded. 

 This intensification proceeds until the cooling reaches 

 the boiling point of hydrogen at the pressure obtaining 

 in P. That pressure is practically atmospheric, since the 

 vessel communicates with the gasholder, which is sealed 

 by a few inches of water. Liquid hydrogen then collects 

 m the lower part of the vessel P. 



One of the results of liquefying^ hydrogen has been to 

 show that helium is a still more volatile gas. It is 

 possible, therefore, to reach a lower temperature than that 

 of liquid — probably even than that of solid — hydrogen 

 by applying to helium the same process of free expansion 

 with intensification by counter-current interchange which 

 has succeeded in liquefying hydrogen. But helium is an 

 exceedingly rare gas, so that the cost of further advances 

 will be very great. Moreover, the most volatile gas 

 probably becomes solid and loses practically all vapour- 

 tension at a temperature above the absolute zero, so that 

 for the attainment of that interesting point no combina- 

 tion of the three methods of cooling above described will 

 suffice. Some fourth system of pumping energy will 

 have to be devised before any portion of matter can be 

 absolutely deprived of heat, and it is for the discovery of 

 this fourth method that onlookers interested in low 

 temperature research are now waiting. 



PROFESSOR TAIT. 



T X the month of February, Prof. Tait, owing to a linger- 

 -'■ ing illness, resigned the chair of natural philosophy 

 in the University of Edinburgh. Since then the graver 

 symptoms of his illness had somewhat abated, and it was 

 hoped that he might live to enjoy some years of rest and 

 relaxation. 



This hope was disappointed by his sudden death on 

 July 4, at Challenger Lodge, Wardie, whither he had been 

 removed for change of air on the invitation of his friend 

 and former pupil. Sir John .Murray. 



The end of his blameless life and brilliant career 

 brings to many an irreparable gap in their circle of 

 friendship, and to the University of Edinburgh the loss of 

 her chief ornament. Of late years Tait had confined him- 

 self more and more to his class work, to the management 

 of the affairs of the Royal Society of Edinburgh, and to 

 the pursuit of his manifold scientific investigations. But, 

 although his direct participation in University affairs 

 diminished, his colleagues never lost the impression that 

 a great man dwelt among them, and not one of them 

 would have dreamed of taking action in a matter likely 

 to interest Tait without considering his opinion. To 

 those who knew him intimately, and therefore loved him, 

 the coming years will never fill his place, although they 

 may alleviate the sense of loss by weaving around it 

 happy memories of flashes of his keen and rapid intel- 

 lect, of the merry geniality and quaint eccentricity of his 

 singularly beautiful character, and of his staunch, almost 

 qui.xotic, devotion to an approved cause or to a friend. 



Tait was in most senses an Edinburgh man. He was 

 born at Dalkeith on .■\pril 28, 1 831. His early education 

 was obtained at the Dalkeith Grammar School, and at 

 the Circus Place School in Edinburgh. Like his name- 

 sake, the late .Archbishop of Canterbury, Tait was a dis- 

 tinguished pupil of the Edinburgh .-Academy ; and loved 

 to tell amusing stories of his mathematical master, Dr. 

 Gloag, whose stern, eccentric character was one of his 

 favourite recollections. .At the University he studied for 

 a session under Kelland and Forbes. The former became 



NO. 1656, VOL. 64] 



his colleague and lifelong friend, and he cherished the 

 memory of the latter even in such insignificant matters 

 as the details of class-certificates and class-examinations ; 

 and, when the priority or credit of Forbes's work was 

 called in question, he defended him with a ferocious 

 knight-errantry that surprised those who knew Tait little 

 and seemed so characteristic and charming to those who 

 knew him well. 



Some of Tait's Academy schoolfellows are still alive, 

 and they speak of him with a mixture of love and respect 

 which shows that he must have been a leading figure 

 among them. Clerk-Maxwell was his most intimate 

 school and college friend, and the friendship thus begun 

 continued to the end of Maxwell's life, absolutely undis- 

 turbed by the fact that the two were rival competitors 

 for the Edinburgh chair in i860. The two men were in 

 truth the Damon and Pythias of British science. Each 

 in his special way was strong in mathematics, both had 

 intense love for physical science, and both were men of 

 wide and varied culture. Each understood perfectly both 

 the strong and the weak points of the other, and both 

 were men of playful disposition and of absolute frank- 

 ness and sincerity. Those who have occasionally seen 

 letters that passed between them will readily agree that 

 their correspondence should be preserved with a view to 

 ultimate publication ; for it would undoubtedly prove 

 one of the most interesting scientific documents of the 

 nineteenth century. 



The promise of the two illustrious Edinburgh friends 

 was amply fulfilled in Cambridge. Tait was senior wran 

 gler and first Smith's Prizeman in 1S52, being then twenty- 

 one years of age, and Maxwell was second wrangler and 

 first Smith's Prizeman, equal with Routh, in 18^4. They 

 were happy in their private tutor, William Hopkins, of 

 whom Tait always spoke with the highest appreciation, 

 and to whose tuition he attributed with characteristic 

 generosity much of the mathematical skill which doubt- 

 less came to him by the grace of God. He often con- 

 trasted the method and spirit of Hopkins' teaching with 

 the work of the modern coach ; but in his depreciation of 

 the latter he perhaps scarcely allowed enough for the 

 brilliancy of Hopkins' pupil and the altered circum- 

 stances of the tutor of to-day. 



Into the boisterous joviality of Cambridge under- 

 graduate life in his time Tait entered fully, and one 

 often envied the boyish zest with which in middle age he 

 would recall the part he had taken in many a college 

 prank at PeterhoLise in his youth. He was, indeed, all his 

 days a sympathiser with the frolics and the foibles of 

 ordinary men, and his stately figure and the genial 

 smile on his rugged, manly face will be as much missed 

 on the green at St. .Andrews and in the smoking room 

 of the " Royal and .Ancient " as it will be in the quad- 

 rangle of the University. Tait was a keen golfer, and 

 for forty years his invariable recreation was an annual 

 holiday at St. .Andrews, which he spent mainly on the 

 links. He watched with great delight the triumphal 

 progress to the championship of his amiable son Freddy, 

 and it was said, probably with truth, that Freddy's fame 

 was dearer to him than his own scientific renown. There 

 is little doubt that Freddy's untimely death in the South 

 African war and the agonising weeks of suspense that 

 preceded the final news of his fate hastened the onset of 

 his father's last illness, and it is certain that it darkened 

 the close of a singularly placid and happy life. 



In 1S54 Tait was appointed professor of mathematics 

 in the Queen's College, Belfast, and there he became 

 acquainted with .Andrews the chemist, and through him 

 with Rowan Hamilton the mathematician. These two men 

 exercised a decisive influence on his future life, and, as was 

 his way, he repaid them both with the tenderest regard and 

 reverence. .Andrews stimulated his love for well-directed 

 physical research, and helped him to cultivate that 

 marvellous power of clearly apprehending and plainly 



