Albert Abraham Michelson

“ Art. XXXVI.—Influence of Motion of the Medium on the Velocity of Light; by Albert A. Michelson and Edward W. Morley. [1]
The only work of any consequence, on the influence upon the velocity of light of the motion of the medium through which it passes, is the experiment of Fizeau. ”

“ Light from a source at a (fig. 5) falls on a half silvered surface b, where it divides; one part following the path b c d e f b g and the other the path b f e d c b g. This arrangement has the following advantages: 1st, it permits the use of an extended source, of light, as a gas flame; 2d, it allows any distance between the tubes which may be desired; 3d, it was tried by a preliminary experiment, by placing an inclined plate of glass at h. The only effect was either to alter the width of the fringes, or to alter their inclination ”

“ In the ether the time would be , hence If now the ether remains fixed while the molecules are in motion, the mean distance traversed between encounters will no longer be , but ; where is the distance the first molecule moves while light is passing through it, and is the distance the second one moves while light is moving between the two. If is the common velocity of the molecules then , and . ”

“ The stream entered each tube by two tubes a, b (figs. 1, 2) and left by two similar ones d, c. The beginning of the column was taken as the intersection, o, of the axes of a and b, and the end, as the intersection, o' , of the axes of d and c. Thus . is found by observing the displacement of the fringes; since a displacement of one whole fringe corresponds to a difference of path of one whole wave-length.
Observations of the double displacement A.
=double displacement ”

“ But Clausius has shown that , where is a constant, the density of the molecule; , that of the substance; and a, the diameter of the "sphere or action." and a are probably nearly constant, hence we have finally . ”