The Philosophical magazine; a journal of theoretical, experimental and applied physics . dent perpendicularly on the ii_first surface A C of a glass prism,and suppose it to issue from a starfrom which the earth is movingdirectly away. It will then pro-ceed without deviation as far asP ]M. For the sake of simplicity,instead of the earth moving andthe rether remaining at rest, sup-pose the earth to be at rest andthe surrounding aither to movewith the velocity C in the opposite direction. The densityof the aether within the prism being, then, to that without, as A cto 1, its rate of motion in the
The Philosophical magazine; a journal of theoretical, experimental and applied physics . dent perpendicularly on the ii_first surface A C of a glass prism,and suppose it to issue from a starfrom which the earth is movingdirectly away. It will then pro-ceed without deviation as far asP ]M. For the sake of simplicity,instead of the earth moving andthe rether remaining at rest, sup-pose the earth to be at rest andthe surrounding aither to movewith the velocity C in the opposite direction. The densityof the aether within the prism being, then, to that without, as A cto 1, its rate of motion in the prism \\\\\ be ---; since the par-ticles of aether, which are at the surface A C at any epoch, musttravel a unit of length from it in the same time that it takes those to the depth -r- in the prism to issue from it, so as to occupy in vacuo a stratum of space a linear unit deep. If, then,IV denote the velocity of light, n the index of refraction, the waveof light VSl, which begins to leave tlie prism at i\I, will move , to cfrom P to N with the velocity —; and if the time it takes. Ann. de Chim. et de Phys. 1818, vol. ix. p. .)(). ^r. F. Eisenlolir an the Vibration of Light. be/, we have lX = — —r-- Meanwhile a circular wave willn A have spread from the point ]\I, and in the time / will haveacquired a radius tw; but at the same time it will have beencarried back a distance ct, so that its centre, instead of beingat M, will be at ]\I, a distance ct within the prism (it beingof course understood that the wave which has issued from theprism remains outside). The position of the emerging ray-is therefore obtained by drawing from N a perpendicular uponthe line MR = /i(?. In order to observe this ray, however, thetelescope must be brought into the position MR; because if MRbe its length, the sether moves from M to M in the same timethat it takes a ray moving in aether at rest to pass over the di-stance MR, so that the ray takes the resultant direction MR. Now the experime
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