THE 
LONDON, EDINBURGH anv DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FOURTH SERIES.] 
APRIL 1860. 
XXXII. On the Effect of the Motion of a Body upon the Velocity 
with which it is traversed by Light. By M. H. Fizzau*. 
| oooh theories have been proposed with a view of accounting 
for the phenomenon of the aberration of light according 
to the undulatory theory. In the first instance Fresnel, and 
more recently Doppler, Stokes, Challis, and several others have 
published important researches on this subject; though none of 
the theories hitherto proposed appear to have received the com- 
plete approval of physicists. Of the several hypotheses which 
have been necessitated by the absence of any definite idea of the 
properties of luminiferous ether, and of its relations to ponder- 
able matter, not one can be considered as established; they merely 
possess different degrees of probability. 
On the whole these hypotheses may be reduced to the follow- 
ing three, having reference to the state in which the ether ought 
to be considered as existing in the interior of a transparent body. 
Either, first, the ether adheres or is fixed to the molecules of the 
body, and consequently shares all the motions of the body ; or 
secondly, the ether is free and independent, and consequently 
is not carried with the body in its movements ; or, thirdly, only 
a portion of the zther is free, the rest being fixed to the mole- 
cules of the body and, alone, sharing its movements. 
The last hypothesis was proposed by Fresnel, in order at once 
* Translated from the Annales de Chimie et de Physique for December 
1859. The original memoir was presented to the Parisian Academy of 
Sciences, Sept. 29, 1851; and a translation of the brief abstract published 
in ie Comptes Rendus was given in the Phil. Mag. for December 1851, 
p- 568, 
Phil. Mag. 8. 4, Vol. 19, No, 127. April 1860. 8 
