166 J. Lovering on Velocity iy Light and the Sun’s Distance. 
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and this displacement increases with the velocity of rotation: it also in- 
creases with the length of the route passed over by the rays, and with 
the gene of the mark from the plane mirro 
call V the het of light, » earl uae of times the mirror 
turns jn a second, / the distance between the plane mirror and the last 
concave mirror, 7 the athe of the ak from the turning mirror, and 
d the observed displacement, we have V = ae 
: an expression which 
gives the velocity of light when the other ero bin are separately meas- 
ured. The distances 7 and r are measured directly by a rule. The devi- 
ation is observ en eae it remains to show how the number 
is mounted directly upon the axis of a small siarting of a well known 
cra bola irably constru a by Froment. The air is er byia bigh 
between these two forces, which tend to equilibrium, cannot fail to re 
ceive and to preuitve a uniform velocity. Any check whatever, a 
upon the flow of the water, allows this velocity to be regulated wi 
wy extensive limits 
“It re 
emains, to estimate the number of turns, or rather to impress OD | 
= teeth appear immovable pore then that the ae idk m te 
circumference, turns once in a second, and that the turbine 
wp. ti. ay fs oer reg er dow of air, the teeth are made to appear 
