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Against this experiment one can argue, that the length of the arms are just too small to obtain any observable displacement of the fringes. But Michelson together with Morley repeated the experiment on a larger scale.^[1] The light rays were traveling forth and back in mutually normal directions several times, because they were reflected every time by mirrors; the latter as well as all other parts of the apparatus stood on a stone plate, that swam on mercury and which could be rotated in horizontal direction. However, the shift as required by Fresnel's theory could not be observed again.

I have sought a long time to explain this experiment without success, and eventually I found only one way to reconcile the result with Fresnel's theory. It consists of the assumption, that the line joining two points of a solid body doesn't conserve its length, when it is once in motion parallel to the direction of motion of Earth, and afterwards it is brought normal to it. If for example the distance in the latter case is $l$ and in the first case $l(1-\alpha )$, then the first expressions (1) and (2) have to be multiplied by $1-\alpha$. Neglecting ${\tfrac {\alpha p^{2}}{V^{2}}}$, one obtains

$2{\frac {l}{V}}\left(1+{\frac {p^{2}}{V^{2}}}-\alpha \right)$

The difference to (2) - and thus the whole objection - would be removed when

$\alpha ={\frac {p^{2}}{2V^{2}}}$

Such a change in length of the arms in Michelson's first experiment, and in the size of the stone plate in the second, is really not inconceivable as it seems to me.

Indeed, what determines the size and shape of a solid body? Apparently the intensity of molecular forces; any cause that could modify it, could modify the shape and size as well. Now we can assume at present, that electric and magnetic forces act by intervention of the aether. It is not unnatural to assume the same for
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1. American Journal of Science, 3d Ser. Vol. XXXIV, p. 383. 1887.