390 A. A. Michelson — Velocity of Light. 
Art. XLVI. — Experimental Determination of the Velocity of 
Light; by AuBerT A. MIcHELSON, Master, U. S. Navy.* 
[Abstract of paper read before the American Association for the Advancement of 
Science. ] 
Ler §, fig. 1, be a slit through which light passes, falling on 
R, a mirror free to rotate about an axis at right angles to the 
plane of the paper; L, a lens of great focal length, upon which 
the light falls, which is reflected from R. Let M be a plane 
mirror, whose surface is perpendicular to the line RM, passing 
through the centers of R, L and M, respectively. If L be so 
placed that an image of S is formed on the surface of M, then, 
this image acting as the object, its image will be formed at 8, 
and will coincide point for point with S. 
L 3 
Ee eR SR | EEE RROD etc rencevacremnememeereeme fae 
U 
< 4 
| 
s 
image at M. This result, namely, the production of a station- 
ary Image of an image in motion, is aeaolatcly essential. It 
was first acco! meg by Foucault, and in a manner differing 
pe 0 Serves but little from the foregoing. 
In this case, L, fig. 2, served simply to form an image of S 
at M; and M, the returning mirror, was spherical, the center of 
_ Curvature coinciding with the axis of ik The lens, L, was 
Placed as near as possible to R. The light forming the return 
ss * Prepared for this place by the Author. 
