162 



SCIENCE, 



[Vol. IV., No. 82. 



theoretical and practical importance is second 

 to none in its bearing on the progress of 

 humanity. 



John W. Strutt, the third of his race bear- 

 ing the title Lord Rayleigh, is the eldest son 

 of John James, second Lord Rayleigh, and of 

 Clara Elizabeth Latouche, daughter of the late 

 Capt. Vicars, R.E. He was born Nov. 12, 

 1842 ; was educated at Trinity, Cambridge, 

 of which he was a fellow. He was married 

 in 1871 to Evelyn Georgiana Mary, second 

 daughter of the late James Balfour, Esq., of 

 Whittinghame, N.B., and succeeded to the 

 title in 1873. 



Lord Rayleigh' s career at the University 

 of Cambridge, which he entered at the age 

 of nineteen, was a distinguished one. He 

 secured the Sheepshanks astronomical exhibi- 

 tion in 1864. The following year he came out 

 senior wrangler and first Smith prizeman. 

 Trinity college thereupon elected him to a 

 fellowship, which he held until his marriage, 

 in 1871. In 1879 he was elected to succeed 

 Maxwell as director of the Cavendish physical 

 laboratory at Cambridge ; and he received the 

 medal of the Royal society in 1882, and was 

 president of section A of the British associa- 

 tion in 1882. This brief record of the im- 

 portant dates in the life of Lord Ra} T leigh may 

 make his life seem uneventful to the ordinary 

 reader ; but the student of his writings will 

 perceive that the years between his acceptance 

 of the fellowship at Cambridge, and his appear- 

 ance as president of the British association for 

 the advancement of science at Montreal, have 

 been eventful in the scientific sense, and full 

 of work. It was no ordinary compliment to 

 a man to be selected as the successor of Max- 

 well. We well remember the commendation 

 pronounced by leading English men of science 

 before Lord Rayleigh became director of the 

 Cavendish laboratory, — ' strong man, Lord 

 Rayleigh ; ' and this simple and peculiarly Eng- 

 lish method of commendation still expresses 

 the truth to-day. An Englishman said to the 

 writer lately, " They question the necessity 

 of the House of lords and the use of lords. 

 Look at Lord Rayleigh ! Cannot we expect 



from this select body of men of hereditary 

 traits and of inherited possessions great things 

 in science, if they will only abandon the subject 

 of franchise bills and the marriage of wife's 

 sisters, and follow the path pointed out by Lord 

 Rayleigh?" 



Lord Brougham, it is true, had scientific 

 tastes, and wrote papers on optics ; but, if one 

 wishes to compare the physical science of 

 Brougham's time with that of the present, and, 

 moreover, to compare the scientific attainment 

 of Lord Brougham with Lord Rayleigh, let 

 him read Brougham's papers, and then turn to 

 Lord Rayleigh' s investigations on diffraction- 

 gratings, and to his various papers on theoret- 

 ical optics. Perhaps his most important work 

 is the ' Theory of sound,' in two volumes, 

 begun on the Nile in 1872, and published in 

 1877-78. This work has received the com- 

 mendation of Helmholtz, and takes the place, 

 in theoretical acoustics, which Helmholtz 's 

 ' Tonempfindungen ' fills in physiological and 

 practical acoustics. 



In looking at Lord Rayleigh 's investigations 

 before the appearance of the ; Theory of sound/ 

 we perceive that he has embodied in this work 

 the special investigations and mathematical 

 work of nearly ten years. Before the appear- 

 ance of this work, the subject of acoustics had 

 been treated in a disconnected manner. There 

 were geometrical, and what might be called 

 sjmthetic, treatises ; but, with the exception of 

 Donkins's 'Acoustics,' there was no generalized 

 and analytical work on sound. What Newton 

 did for mathematics, when he discovered the 

 method of fluxions, or the principles of the 

 differential and integral calculus, Lord Ray- 

 leigh has* done for sound. He has bridged 

 over, so to speak, angular intervals, has filled 

 up discontinuities, and has made the general 

 treatment of acoustical equations flexible. In 

 reading this treatise, one speedily finds that it 

 is not a narrow or limited one. The entire 

 range of modern mathematics is emplo} T ed ; 

 and the system of generalized co-ordinates 

 receives, in this treatise, perhaps the greatest 

 exemplification of its power. One cannot read 

 the treatise who has not become familiar with 



