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LXI. On the Theory oj Experiments to detect Aberrations 

 of the Second Degree. By Edward W. Morley, Ph.D., 

 LL.D., Professor in Western Reserve University, and 

 Dayton C. Miller, Ph.D., Professor in Case School of 

 Applied Science. Cleveland, Oliio *. 



[Plate IX.] 



IX 1887 Michelson and one of the present writers made an 

 experiment " On the Relative Motion of the Earth and 

 the Luminiferous JEther " f- We found that, if there were 

 any effect, it was not sensibly larger than one-fortieth of the 

 amount expected. To explain this result, FitzGerald and 

 Lorentz suggested that the motion of translation of a solid 

 through the a?ther produces a contraction in the direction of 

 the drift, with extension transversely, the amount of which 

 is proportional to the square of the ratio of velocities of 

 translation and of light. 



Such a contraction can be imagined in two ways. It may 

 be thought to be independent of the physical properties of 

 the solid and governed only by geometric conditions; so that 

 sandstone and pine, if of the same form, should be affected 

 in the same ratio. On the other hand, the contraction may 

 depend upon the physical properties of the solid ; so that 

 pine-timber would doubtless suffer a greater compression 

 than sandstone. If the compression annul the expected 

 effect in one apparatus, it may in another apparatus give 

 place to an effect other than zero, perhaps with the contrary 



\\ <■ have now completed an experiment in which two 

 different pine-structures have been used, and in which the 

 optical parts have been so enlarged as to produce an effect 

 2'S times as great as the apparatus of 1887. The object was 

 to determine whether there is any difference between the 

 behaviour of sandstone and of pine. 



When Michelson and Morley got a null result in 1887, it 

 was thought sufficient to give the theory for merely the 

 maximum and the minimum expected in the four principal 

 azimuth-, without mention of the phenomena at intermediate 

 azimuth-. The theory also neglected powers higher than the 

 second of tin- ratio of the velocities. Recently, Dr. Hicks J 

 has published a profound and elaborate discussion of the 

 theory, obtained by methods which are not approximate. 



* Communicated by the Authors. Head at the New York Meeting 

 of the National Academy of Sciences. 

 \m. Jour. Sci xxxiv. p. 838. 

 t Phil. Mag. [&] iii. p. 9(1902). 



Phil. Mao. 8. 6. Vol. 9. No. 53. May 11)05. 2 Y 



