Earth's Motion on the Rotation of a Refracted Ray. 599 



Differences in 

 Micrometer Settings. 



+ -32 ^ 



+ -46 Aug. 4, 1905. 



+ -12 } 11 h. 53 m.— 12 h. 4 in. 



4- -40 West to East, 



-•04 J 



- -50 -\ 



- -30 Aug. 4, 1905. 

 -•18 V 5 b. 21m.— 5 h. 31m. 



+ -52 East to West. 



-•02 J 



+ -24 -j 



+ -38 Aug. 5, 1905. 



+ -28 } 11 h. 58 m.— 12 h. 8 m. 



- -04 East to West. 

 + -28 J 



+ •56 ) 



- -52 Aug. 7, 1905. 

 -•70 V llh. 58 m.— 12 h. 8 m. 

 4- -18 East to West. 



- 32 J 



We have as the mean value o£. the noon setting, 

 W — E=+*14 of a division of the micrometer drum ; and 

 W — E= — "11 of a division of the micrometer drum for the 

 afternoon settings. Reducing, we have 



+ -14 x -02 x 5°/4'2=: +0°-0033 



and -'11 X -02 x 5°/4-2= -0°'0026 



The mean value of the noon deviation + o, 0033 is thus over 

 seven times smaller than the calculated value + o, 024. The 

 fact that this mean value is of the same sign as that which 

 Fizeau calculated, I do not consider of any significance, as, 

 with a sufficient number of observations, this mean would 

 probably have vanished. Nor do I attach any significance 

 to the fact that the afternoon results show a negative mean. 

 These residuals are quite within the limits of experimental 

 error. 



We may therefore conclude that the azimuth of a polarized 

 ray, reflected along the line of drift, is not affected by the 

 motion of the earth through space, at least, to the first order 

 of small quantities. 



Physical Laboratory, University of Nebraska, 

 Lincoln, August 9, 1905. 



