680 Profs. Morley and Miller: Report of an Experiment 



paragraph, which is entirely distinct from the rest of the 

 discussion, he uses an expression which is not sufficiently 

 approximate; e. c/., if the expression be taken to mean the 

 wave-length as stated above, and accordingly used to com- 

 pute the number of waves in a given length in the line of 



vision, it differs from the truth by -~, precisely doubling 

 the result found otherwise. * 



We assert, then, that the theory of 1887 is correct to terms 

 of the order retained, which were sufficient ; that Dr. Hicks's 

 theory agrees with it precisely as to numerical amount and 

 sign* of the effect, and that a third examination of the theory 

 gives results differing from those of the two others only by 

 negligible terms of the third order. 



A 



LXII. Report of an Experiment to detect the FitzGerald- 

 Lorentz Effect. By Edwakd W. Morley, Ph.D., LL.D., 

 Professor in Western Reserve University, and Dayton C. 

 Miller, Ph. D., Professor in Case School of Applied Science^. 



[This experiment was assisted by a grant from the > Rurnford Fund of 

 the American Academy of Arts and Sciences ; and a f idler account will 

 appear in the Proceedings of the Academy.] 



[Plate X.] 



NULL result was obtained in 1887 J in an experiment 

 to detect, if possible, a difference of velocity of light in 

 different directions, owing to the motion of the apparatus 

 towards or away from waves of light in the stationary aether. 

 FitzGerald and Lorentz then suggested that the dimensions 

 of the apparatus might be modified by its motion through the 

 aether. If this modification depend on the resilience or 

 other physical properties of the materials, it may perhaps 

 be detected by experiment. 



We have constructed two apparatus with which to examine 

 this question. In the first, we replaced the sandstone used 

 in 1887 by a structure of white pine. A strong cross was 

 built up of planks, 14 inches wide and 2 inches thick, and 

 14 feet long. One was laid east and west, then one across 

 it north and south, and so on. They were slightly notched 

 where they crossed. On their intersection was secured a 

 cast-iron bedplate for certain optical parts of the apparatus. 



* Taking into account a note in 'Nature,' vol. lxv. p. 343 (1902). 



t Communicated by the Authors : read at the New York Meeting of 

 the National Academy of Sciences. 



t " On the Relative Motion of the Earth and the Luminiferous JEther." 

 A. A. Michelson and E. W. Morley, Am. Journ. Sci. vol. xxxiv. p. 333. 



