Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 309
al construction. This is called thereflex zenith tube, shown in Fig. 131. It is a sec-tional drawing of one of those instruments showingthe path of the rays of light. a, b, is an object- 286 STARGAZING : PAST AND PRESENT. [book iv. glass, fixed horizontally, and below it is a trough ofmercury, c,… … Fig. 131.—Keflex Zenith Tube. after having been reflected from the surface of themercury, and also by the diagonal mirror or prism, g ;at F, therefore, we have an image of the star, whichcan be examined together with the cross-wires at theeyepiece, m. There is in this instrument no necessity CHAP.…
Astronomy · Telescopes
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