226 Professor Joseph Larmor [May 1, 



and entangled materials, the world owes him its highest gratitude. 

 Helmholtz goes on to contrast the universal outlook of such a book, 

 involving unavoidable lacunae and difficult transitions, with the 

 beautiful precision of the best special treatise of the earlier period. 

 But the reader who does not spare himself the necessary effort towards 

 mastery reaps an ample reward ; he will find himself trained and 

 equipped for the task of appreciating and extending knowledge, to a 

 degree that he could never have attained from mere passive assimila- 

 tion of sharply cut formal demonstrations. Valuable to the same 

 end is the constant endeavour of such a work to employ those mathe- 

 matical methods that keep close to actuality, are amenable to detailed 

 interpretation ; though they are naturally much harder, especially 

 at first, than a strictly ordered analytical calculus would be, there 

 remains the permanent gain of direct insight into the processes and 

 relations of nature. Finally, allusion is made to difficulties encoun- 

 tered by the translators, arising from the originality of the treatment, 

 and the series of new scientific terms that the authors had, in con- 

 sequence, introduced. 



This appreciation, by the most competent living master, set out 

 justly the advantages and defects of Thomson's method of work. 

 He never had time to prepare complete formal memoirs. It was but 

 rarely that his expositions were calculated to satisfy a reader whose 

 interests were mainly logical ; though they were almost always 

 adapted to stimulate the scientific discontent and the further inquiry 

 of students trained towards fresh outlook on the complex problem of 

 reality, rather than to logical refinement and precision in knowledge 

 already ascertained. Each step gained was thus a stimulus to further 

 effort. This fluent character, and want of definite focus, has been a 

 great obstacle to the appreciation of " Thomson and Tait," as it is 

 still to Maxwell's " Electricity," for such readers as ask for demon- 

 stration but find only suggestion and exploration. There is perhaps 

 nothing that would contribute more at present to progress in physical 

 thought than a reversion, partial at any rate, from the sharp limita- 

 tion and rigour of some modern expositions to the healthy atmosphere 

 of enticing vistas which usually pervades the work of the leaders in 

 physical discovery. With increased attention to the inspired original 

 sources of knowledge the functions of a teacher would be more than 

 ever necessary, to point to the paths of progress and to contrast the 

 effectiveness of different routes, as well as to restore valuable aspects 

 which drop away in formal abstracts ; science would thus adhere to 

 the form of a body of improving doctrine rather than a collection of 

 complete facts. 



The establishment of significant terminology in dynamics was 

 made still more effective by material illustration' of the principles 

 thus connoted. For example, the law of conservation of rotational 

 momentum, of which" the'germ was already in the Prmcipia, had been 

 developed by d'Alembert and Laplace into complex formulas which 



