Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 250
Those who have looked through acrystal of Iceland spar, Fig. 108, have seen two imagesof everything looked at when the crystal is held in cer-tain positions, but the surfaces of the crystal can be cutin a certain plane such that when looked through, theimages are single. For the micrometer… … Fig. 108.—Double images seeu through Icelaud spar. or other double refracting substance, it is divided up intotwo portions, one of which is refracted more than theother. If we trace the rays proceeding from a point s, Fig.
Astronomy · Telescopes
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