xxu 



which he afterwards published in the sixth volume of the * Edinburgh 

 Philosophical Journal'), that this paper has had little influence on the 

 practice of British workmen, who then and now are far behind the require- 

 ments of the age in the knowledge of geometry. 



It is evident that when he wrote this memoir Herschel did not accept 

 the wave-theory ; but in 1830 appeared in the ' Encyclopaedia Metropoli- 

 tana' his Treatise on Light, where it is brilliantly developed. In this work, 

 which is still read with admiration and profit, the first part is an excellent 

 system of ordinary optics, in which is included the substance of the pre- 

 vious memoir: then he states the emission and wave-theories of Light, 

 applies each of them to explain the laws of reflection and refraction and 

 the phenomena of Newton's rings and diffraction^ fringes, states the ob- 

 jections to each, and shows the superiority of the latter as irresistible. 

 He next describes with singular clearness the phenomena of Polarized 

 Light (not a few of which were discovered by himself,), and gives their 

 theory; and completes the work with the absorption of light and the 

 effect of mechanical force on the optical properties of transparent media. 



In other departments of science it must suffice to notice his investiga- 

 tions of the hyposulphites, to which photography is so deeply indebted ; 

 his researches on photography, including some curious and beautiful 

 processes, and of which it may be remarked that he very nearly antici- 

 pated Mr. Fox Talbot in the discovery of the paper process ; and his 

 invention of the Actinometer. Nor is to be forgotten that on several oc- 

 casions he gave powerful aid to the establishment of those simultaneous 

 magnetic surveys which, under the auspices of Sir Edward Sabine, have 

 thrown such light on the study of terrestrial magnetism. 



It remains to say a few words as to his personal character ; for a man, 

 however high and varied his knowledge of physics or geometry, is a very 

 imperfect specimen of his race if he be deficient in those higher qualities 

 which should regulate morals and the duties of life. Herschel could abide 

 this test. He was deeply and unostentatiously religious ; exemplary in 

 all the social relations. If his devotion to his father might seem exces- 

 sive, it should be remembered what a man that father was. Far above 

 the petty jealousies which haunt meaner minds, he was always ready to 

 do the fullest justice to the labours of others, regarding them as fellow- 

 labourers in a great work, not as rivals ; and when it was his lot to be 

 engaged in controversy, which he avoided as much as possible, he never 

 allowed it to hurry him into any thing unworthy of a Christian gentleman. 

 A beautiful trait in his character was the interest he took in those who, as 

 yet unknown, were beginning to climb the ascents of science, and the en- 

 couragement he was always ready to afford them. One instance of this 

 which it was the writer's lot to witness struck him so much that he ventures 

 to mention it here. At an early meeting of the British Association a rough- 

 looking man brought forward a paper on the strength of iron; unaccustomed 

 to such an audience ? his presence of mind failed, and he sat down muttering 



