48 



NATURI-: 



[November 9, 191 1 



of ideas which formed the thread of his discussions. 

 These, sad at heart, ihouj^^ht sinipi} ol ilxii 

 and wond-nd hwu ilny were }<oin{^ \u vurn 

 inalhemalic.il li;nriii. ('hrxstal liad lar uih. i (-ui- 

 ccptions ill lii^ luiiid; but witli all hi^ slrcmuui-- ;iik1 

 succi'ssful labours to raise tlie staiidaid ot iiiath<'- 

 iiiaiical iraching he was essentially just, and kn<\v 

 u. 11 that minds of the highest quality are not always 

 .tblr to appreciate the convergency of series or the 

 nivsiiiii's of probabilities. When the time for testing 

 came, the really intelligent, hard-woikin^ student i^ol 

 lull ereilii l()i- his limited mathematie.d jjowiTv. 



It was a i;i'eat pleasure to see in ilieNi^ early (la\.s 

 the eiiihusiasiii of the mathematical sludenls, lor 

 whose sakes (hrxsial never Spared himself. The 

 'coaches," all alive to the necessities of the situation, 

 quickly got hold of the methods; and as th. -raduatf s 

 passed out into the schools they carried with ihem 

 the mind of their master. To Chrystal, more than 

 to any other, the great development of mathematical 

 t. ac hiiii^ ill the schools may be traced. 



Iruiii tile first, as Tait never failed to remind us, 

 ( lirsstal'v was essentially a physical mind. As a 

 (ainhrid-e uiuleri^raduate he had — as some thought — 

 '■ wasted " his time with Maxwell in the Cavendish 

 Laboratory, fiddling with wires, when he should have 

 Ix'en practising the writing out of problems. His 

 careful investigation into the truth of Ohm's law is a 

 standard piece of work showing clear perceptions and 

 carelul niani|)ulat ion. The articles on "Electricity" 

 ;iiid " M.ie;netisni ■■ in the ninth edition of the "En- 

 cyclopaedia Hriiannica" contain in a wonderfully small 

 compass the very best up-to-date account of these 

 sciences, both theoretical and experimental, ever put 

 together. Had they been printed in book form a few 

 >(ars after their first publication they would have 

 been the vade mecum of the advanced student. Their 

 merits are a clear, flowing, forceful style, and a re- 

 markable discrimination in selecting material. The 

 great advances of the last twenty years have been 

 along the lines clearly indicated in these articles. On 

 coming to Edinburgh, Chrystal, though he gave his 

 principal attention to his real class work, did not 

 allow his physical work to fall behind. There was 

 no %ummer session in those days ; and the summer 

 months which most other professors spent in holiday 

 were spent by Chrystal in Tait's laboratory. Here he 

 brought to full fruition his theory of the differential 

 telephone. His paper on the subject is published in the 

 Transactions of the Royal Society of Edinburgh, and 

 constitutes the first truly scientific discussion of the 

 action of the induction-balance. 



Outside his own particular experimental work, 

 Chrystal was an ever-present source of inspiration to 

 the students. Several of the investigations which 

 were carried through in Tait's laboratory during the 

 early 'eighties were suggested by Chrystal, who really 

 acted the part of a second professor of natural 

 philosophy. With the increasing care of his own 

 department, he was compelled after a few years to 

 give up his experimenting. Another reason, as he 

 once expressed it, was that he found he was usurp- 

 ing the use of all the best instruments in the place, 

 so that the students were not able to get their best 

 work done. 



The personality of Prof. Chrystal soon made itself 

 felt on board and senate. He was elected a vice- 

 president of the Royal Society of Edinburgh in 1887, 

 at the unusually early age of thirtv-six. For two 

 terms of six years he filled the same "important post, 

 and, in iqoi. on Prof. Tait's death, he was chosen 

 general secretary. The duties of this office he per- 

 formed in a manner which it is impossible to praise 

 too highly. Only a man of Chrystal's alertness of 

 mind, clearness of vision, knowledge of affairs, fair- 

 NO. 2193, VOL. 88] 



mindedness, and yet determination to have the 

 society's rii^his recognised, could have successfully 

 manaani 'I ih.- society through the time of strain 



when ii- siaius and etficiency were threaten«-d. Th' 

 Seniiisii nn inb( rs (;l Parliament stood loyally by th' 

 s<i(ieiv, and by their sympathy more was achieved 

 than w.as .it first hojjed for. 'Ihrough all the cross- 

 currents of opinion, it was Chrjstal who was the real 

 steersman. The present habitation of the Royal 

 Society of Edinburgh is a lasting monument to th' 

 memory of its general sicretary, who secured froi: 

 the GovL-rnnicnt of the day a generous recognitioi. 

 of the claims of science. fl 



The same keen personality combined with business^ 

 faculties of a high order made Chrystal the right man 

 in the right place, when in i8qi his colleagues elected 

 him the dean of the faculty of arts. The new- 

 ordinances which came into etlect at that time were 

 soon found to be hampering and unworkable in the 

 interests both of teacher and 'pupil. Strenuously 

 Chrystal applied himself to the 'reorganisation of the 

 whole arts curriculum, and the reward of his labours 

 he lived to see in the sanctioning of a new ordinance 

 which grants autonomy to each university within 

 reasonable limits. 



To these administrative duties he added for some 

 years the chairmanship of the Provincial Committee 

 for the Training of Teachers, lie was, in fact, the 

 first chairman, and probably did more than any other 

 single man to mould this committee into a serviceable 

 administrative body. He was also for several yean 

 a tTKMiiber of the committee appointed by the W 

 Office to advise the Army Council regarding the pn 

 liminary education of officers. 



With all this administrative strain. Chrystal con- 

 tinued to develop his department of mathematics to 

 greater and greater effectiveness. His text-books on 

 algebra are well known; but it is not perhaps so well 

 known that he was the inventor of the very appro- 

 priate phrases the " freedom equations " and the 

 "constraint equation " of a curve. These show again 

 how his mind moved in dynamical regions. 



Chrystal's literary output is perhaps smaller in 

 quantity than that of most men of equal reputation; 

 but the quality is high. He communicated to the 

 Edinburgh Mathematical Society an admirable account 

 of the properties of lenses and doublets, to the study 

 of which he was led in his recreation as a photo- 

 grapher. He was very skilful in all photographic 

 manipulation, his attachment to the art dating from . 

 his Cambridge days, when dry plates were unknown. 



In addition to several mathematical papers in the 

 Proceedings and Transactions of the Royal Society 

 of Edinburgh, he enriched the science of hydro- : 

 dynamics by his researches on seiches. His attention 

 was directed to the subject by Sir John Murrav, 

 and the whole problem, experimental and theoretical, 

 seized hold of his mind in a marvellous way. This 

 recent work is too well known to need discussion now. 

 Not only did he vastly improve the mathematical 

 theory of these movements in lakes and bays, but he 

 invented instruments and obtained records which shed 

 a new light on the whole set of phenomena. The 

 work is stamped with all the thoroughness and in- 

 genuity of a fine intellect. 



What Chrystal undertook to do he djd to the utmost 

 of his powers. He left no ragged ends. All was car- 

 ried through with celerity, yet with thoughtfulness 

 and accuracy. Quick in his apprehension, and im- 

 patient of humbug, he was a terror to the student 

 who was not an honest seeker after truth, but to the 

 genuine student he gave of his best, and nothing 

 delighted him more than when a pupil showed 

 originality and power of research. His knowledge of 

 human affairs was wide and deep. He was splendid 



