March 3, 1905.] 



SCIENCE. 



337 



Circular Dichroism in Natural Eotary 

 Solutions. D. B. Brace and W. P. 

 McDowell, University of Nebraska. 



Electric Douhle Eefraction in Liquids Un- 

 der Loxv Electric Stresses, and also at the 

 Boiling Point. D. B. Brace, G. W. 

 Elmen and L. B. Morse, University of 

 Nebraska. 



TJie. Electrotnagnetic Theory and the 

 Velocity of Light. Henry T. Eddy, 

 University of Minnesota. (To be pub- 

 lished in the Physical Review.) 

 j\Ir. iMills has recently published a 

 paper* in which he has given the results 

 of measurements made by him of the in- 

 crease in the velocity of circularly polar- 

 ized light in bisulphide of carbon along 

 the lines of force in a magnetic tield. Em- 

 ploying circularly polarized light, he was 

 successful in obtaining a difference of one 

 or more wave-lengths between two rays 

 circularly polarized in opposite senses, 

 one ray having its velocity increased while 

 the other was decreased, and this was ob- 

 tained with apparatus with which no dif- 

 ference whatever was observable in case 

 of plain polarized rays. 



The apparatus mentioned is a form of 

 interferometer devised by Professor Mor- 

 ley and paid for by a grant made by the 

 American Assoeiation for the Advance- 

 ment of Science for the purpose of investi- 

 gating certain points to which the present 

 writer had taken exception in the theory of 

 the Faraday effect as developed by Pro- 

 fessor Rowland, f who had attempted to 

 account for the twisting of the plane of 

 polarization of plane polarized light while 

 being propagated along the lines of force 

 in a magnetically active medium by the 

 action of the Hall effect in the medium. 

 As just stated, the present writer found 

 himself unable to agree with that part of 

 * Phxjs. Rev., Vol. XVIII., p. 65, Feb., 1904. 

 t Am. Jour. Math., Vol. 3, p. 109, 1880. 



Professor Rowland's most valuable theo- 

 retical treatment of the Hall effect which 

 related to rotary polarization. After a 

 full presentation of the theoretical ques- 

 tions involved at the Toronto meeting of 

 the American Association for the Advance- 

 ment of Science, in 1889, the apparatus 

 was constructed, and after many delays a 

 final report was presented to the American 

 Association for the Advancement of Sci- 

 ence, at the Boston meeting, August, 1898. 

 The report was duly published* and con- 

 tains, first, the present writer's theoretical 

 developments and computations as to the 

 possible increase or decrease in velocity to 

 be looked for in case of magnetic twisting 

 of the plane of polarization, and second, 

 a full description by Professor Morley of 

 his apparatus and a detailed account of 

 the experimental work by Professors Mor- 

 ley and Miller, who worked in collabora- 

 tion. No experimental change in the 

 velocity of plane polarized light could be 

 detected with this apparatus, and the 

 numerical computations just mentioned 

 showed in fact the possible change in the 

 velocity to be too minute to be detected by 

 the apparatus as used. Although such is 

 the fact with plane polarized light, the ex- 

 periments of Mr. Mills show that such is 

 not the fact with circularly polarized light. 

 Moreover, it will be shown theoretically 

 that in case of circularly polarized light 

 the amount of change in velocity due to 

 the magnetic field is expressible as a lower 

 power of small quantities, than in case of 

 plane polarized light, and consequently the 

 magnitude of the change in the former 

 case is large compared with the latter, and 

 in fact varies as the square of the latter; 

 and while the latter may be quite beyond 

 the range of observation, the former may 

 be well within it, as the experiments of 

 Mr. Mills have proven. 



In view of this it is the aim of this paper 



* Phys. Rev., Vol. VII., p. 282, December, 1898. 



