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SCIENCE. 



[N. S. Vol. XXIII. No. 579. 



land spar; and the doubts of the director 

 of the realization of the demonstrated con- 

 ditions, even if they could be proved pos- 

 . sible in theory. After Brace had suc- 

 ceeded in experimentally obtaining the con- 

 ditions which his theory called for, he ap- 

 plied them to the examination of the ques- 

 tion of the transmission of a polarized ray 

 in a magnetic field. He was not able at 

 that time to answer the question which he 

 had in mind, but he was able to produce a 

 memoir full of discoveries and ingenious 

 suggestions, which culminated many years 

 afterward in his final resolution of the 

 problem, by the actual separation of the 

 plane polarized ray in a magnetic field into 

 two circularly polarized components. 



Brace took his doctor's degree in 1885. 

 After a short service at the University of 

 Michigan, he became, in 1888, professor of 

 physics at the University of Nebraska, 

 where he devoted himself, with the con- 

 scientious fidelity which was a part of his 

 nature, to the duties of his position. These 

 duties he did not interpret in any narrow 

 sense. He conceived that it was a large 

 part of the obligation, which lay on him, 

 to promote the progress of physics, not 

 only by his own researches, but by organ- 

 izing and assisting a corps of fellow work- 

 ers. By his enthusiastic zeal, and by the 

 wise administration of the facilities afl'ord- 

 ed him, he was able to draw around him a 

 number of men who caught inspiration 

 from his spirit, and who have, by their 

 published researches, for several years past, 

 been giving to the institution in which they 

 worked an honorable prominence. 



In the midst of his official duties Brace 

 gave what time and strength he could spare 

 to his own investigations. His mind was 

 exceedingly fertile in the invention of 

 methods of observation. The subject of 

 optics, in which his first original work had 

 been done, remained the subject of his 

 choice throughout his life. As that science 



has developed in connection with certain 

 theories of electricity, fundamental ques- 

 tions have arisen, principally relating to 

 the general subject of the relative motion 

 of matter and the ether, which can only be 

 answered by carrying observation to a de- 

 gree of refinement which was not attained 

 in the classical experiments of the great 

 French and English investigators. Brace 

 was profoundly interested in this great sub- 

 ject, and his principal task, for several 

 years, was to improve the methods of ob- 

 servation to such a degree that indubitable 

 conclusions might be drawn in regard to 

 the results of experiments left doubtful by 

 earlier investigators. By the union of in- 

 ventive power with great experimental skill 

 he succeeded in extending the range of ob- 

 sei'vation in his repetitions of the experi- 

 ment of Lord Rayleigh, to test for possible 

 double refraction in an isotropic medium; 

 the experiraent of Mascart, to test for 

 a difi^erential effect on the natural rota- 

 tion of the plane of polarization; and the 

 experiment of Pizeau, to test for a possible 

 change in the azimuth of the plane of 

 polarization of a ray, polarized by refrac- 

 tion, to so high a degree of accuracy as to 

 be able to confirm with confidence the nega- 

 tive results of Rayleigh and Mascart, and 

 to assert with equal confidence that the 

 positive result, which Fizeau believed he 

 had obtained, must have been due to some 

 experimental error and not to the cause 

 to which it is sometimes ascribed. He had 

 in mind other experiments to test the same 

 general question, and we who knew the rare 

 combination of powers which he possessed 

 did not even despair of his succeeding in 

 making the final test which is necessary, by 

 the determination of the velocity of light 

 when transmitted in one direction only. 



This is not the place to enumerate 

 Brace's contributions to science. It is suf- 

 ficient to notice that part of his work in 

 which his activity culminated, and which 



