February 2, 1906.] 



SCIENCE. 



163 



was most closely connected with his hopes 

 for the future. All his other work showed 

 the same distinguished qualities; unusual 

 ability of invention, great experimental 

 skill, and the faculty of choosing central 

 subjects to which to devote his powers. 



Brace was for several years a member of 

 this association, and was vice-president and 

 chairman of Section B for the year 1901-2. 

 He was also a member and vice-president 

 of the Physical Society, and considering 

 the distance between his home and the 

 usual place of meeting of that society, a 

 freqtient attendant at its meetings. He 

 very greatly enjoyed the opportunities af- 

 forded by them to meet with his friends. 

 Under a somewhat retiring manner he con- 

 cealed a warm heart and a sincere and un- 

 selfish admiration of other men's abilities 

 and successes. His encouragement and 

 sympathy were always given to those who 

 came to him to talk about their scientific 

 projects; and it renews my own sense of 

 bereavement when I recall the cordial way 

 in which he discussed with me the subject 

 of the present address. His life of untir- 

 ing devotion to duty and of genuine good- 

 ness will always remain a sweet memory 

 to his friends; as his lofty and unselfish 

 zeal for the promotion of knowledge will 

 be an example and a stimulus to those who 

 know the story of his work. 



In the retrospect of the progress of phys- 

 ics during the past year, the attention is 

 first and most forcibly attracted to the 

 work which has been done in the general 

 subject of radioactivity. By the continued 

 labors of J. J. Thomson and of those in 

 his immediate circle of fellow-workers, of 

 Rutherford and Bragg, of Lenard and 

 Kauffmann, and of many others, our knowl- 

 edge of the details of the radioactive proc- 

 ess has been very much extended. Some 

 progre.ss, though not so great, has been 

 made in the development of the theory. 

 But the main result, which, it seems to me. 



can be considered as attained during the 

 year, is the final appreciation of what we 

 may call the electrical theory of matter, or 

 at least of the possibility of explaining the 

 properties of matter, even those of the most 

 fundamental character, by the laws of elec- 

 tric action. Of course such an explanation 

 can not yet be given, but it seems to me 

 that, so far as we can judge by the hints 

 and the obiter dicta which appear from 

 time to time, the belief in the ultimate pos- 

 sibility of such an explanation has at last 

 become general. 



I doubt if the history of science affords 

 another instance of so fundamental a 

 revolution in modes of thinking, occurring 

 in so short a time. For it is only ten years 

 ago that Rontgen discovered the peculiar 

 radiation that is known by his name, and 

 I think we may fairly date the beginning 

 of the study of radioactivity from that 

 important discovery. On the one hand, the 

 facility with which gases can be ionized by 

 the Rontgen rays aided J. J. Thomson 

 materially in his study of ionization, which 

 led to his discovery of the electron and his 

 investigation of its properties. On the 

 other hand, the fluorescent effects of the 

 Rontgen rays incited Becquerel to his ex- 

 amination of uranium, and led to his dis- 

 covery of its radioactive properties; and 

 from this to the isolation of radium by 

 M. and Mme. Curie, and to the splendid 

 series of researches which have been car- 

 ried out on that substance and on other 

 allied substances, the way is clear. Ront- 

 gen 's discovery was made only ten years 

 ago, and it is a marvelous illustration of 

 the large sum of human effort applied to 

 the study of science, and of the active, I 

 might almost say the radical, tendency of 

 the modern mind, that in so short a time 

 we have obtained so great a body of estab- 

 lished knowledge, and experienced so com- 

 plete a revolution in our most fundamental 

 modes of scientific thought. 



