On the relative motion of the earth and the luminiferous æther

THE LONDON, EDINBURGH and DUBLIN PHILOSOPHICAL MAGAZINE AND JOURNAL OF SCIENCE.
DECEMBER 1860.
On the undulatory theory, according to Fresnel, first, the æther is supposed to be at rest except in the interior of transparent media, in which secondly, it is supposed to move with a velocity less than the velocity of the medium in the ratio
, where
Let
, fig. 1, be a ray of light which is partly reflected in
, and partly transmitted in
, being returned by the mirrors
and
, along
and
is partly transmitted along