164 J. Lovering on Velocity of Light and the Sun’s Distance. 
equally applicable to light and to electricity. If a wheel finely 
cut into teeth on its circumference is put in rapid rotation, a ray 
of light, which escapes between two consecutive teeth, wi ill after 
being reflected perpendicularly by a mirror, return to strike the 
wheel at a different point, and either be intercepted by a tooth 
. or admitted at another interstice. Suppose the velocity of the | 
wheel just sufficient to bring the adjacent tooth to the position 
whence the ray first started, in the time which the light occupies 
in going to the mirror and returning, In this time the wh 
as moved over an angle found by dividing 360° by twice the 
number of teeth which the wheel contains. Therefore the time 
teeth, and the slowest velocity which produced peachiahee bs 3 
ane 6 turns a second, it —, rie light required ;;}s7 : 
to go 8633 metres and return. Hence its velocity was : 
313, "O74 308 metres or 194, 667 x tiie a second, The Fre 
Academy thought so favorably of this attempt that they refer- 
red the subject to a scientific commission consisting of J 
6; he Pouillet and Regnault, with authority to procure a ' 
machine for repeating the experiment. | 
sea Arago advocated the claims of Wheatstone to the va 
cant place of Corresponding Member of the French A [oS 
in the pet of Physics, it was objected that Wheatstone 4 
only made a single experiment without having discov: oe 
principle, Ara ed to prove that the candidate hadi 
troduced a fertile method of experimentation ag: abe be 
felt in other sciences as well as electricity. For example: @ 
gas scular theory of light requires that the veloanieh of light ie 
ifferent media should vary directly as the Raper of refrae 
tion, whereas the undulatory theory inverts this ra Arago 
prepared for the trial by experiments on rapid oe theme 
chanical difficulties to be overcome, and the comparative advan- 
tage of slower rotations assisted by several reflexions, in > Bae ee 
_ of a single mirror turning with its maximum s Aided by 
the refined skill of Breguet, he realized velocities in the mirror — 
of 1 eh as eee eee the mir- — 
it 
