332 PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 



experiment to the progress of optical theory can hardly be over- 

 estimated. The luminiferous ether was devised or imagined to 

 explain the phenomena of light. Given, that light is an undulatory 

 motion, there must be some medium which undulates. The 

 properties of this medium can be inferred only from the 

 phenomena themselves, but so well did the properties agree, as 

 deduced from different phenomena, so definite and exact were 

 the explanations which the ether afforded, that most students of 

 the subject had come to look upon it as a fact, not a theory, as 

 one of the basal, fundamental facts of our universe. If the ether 

 is stationary, as postulated by Fesnel, the optically important 

 phenomenon of aberration is completely explained, but the Mich- 

 elson-Morley experiment appeared to show that this hypothesis 

 is untenable, and left aberration without the shadow of an ex- 

 planation. It is easy to see that the whole elaborate structure of 

 the ether is shaken and liable to destruction. There was much 

 discussion. Fitzgerald in England, and Lorentz in Holland, 

 nearly at the same time, made the same suggestion, as a possible 

 way out of the difficulty. The mirrors of the interferometer in 

 the Michelson-Morley experiment had been mounted on a block 

 of sandstone, which in its turn was floated in a circular trough 

 of mercury, so that it could be easily rotated in a horizontal 

 plane, in order that the two arms of the interferometer might 

 be brought in turn into the direction of the earth's motion. Fitz- ' 

 gerald and Lorentz suggested that the dimensions of the block 

 of sandstone were altered by its drift through the ether, that 

 in fact, thei stone was shorter in a given dimension when that 

 dimension lay in the direction of the earth's motion in space, 

 than when it lay at right angles to this motion. 



The difficulty, the very desperateness of the situation is 

 shown in the fact that this extraordinary suggestion was seized 

 upon as not improbable. There was a possibility that it might 

 be tested experimentally. All substances might experience such 

 a deformation as they drifted through the ether, but it was con- 

 ceivable that they might not be all deformed alike, that a soft 

 and yielding substance like wood might suffer a different amount 

 of shortening from that of stone or iron. 



