Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 83
A B, we should,describe a solid figure, and if we suppose all the anglesrounded off, so that it is made thinner and thinneras we recede from the centre, the prism system is turned CO STARGAZING : PAST AND PRESENT. [book II. into a lens having the form represented in Fig. 24. Ina simikxr manner,… … Fig. 23.—Fornuttion of a Lens from Sections of Prisms. combinations of curves can be made, some of whichappear in Fig. 26. The action of such lenses upon the light proceed-ing from any source may now be considered. If thereis a parallel beam proceeding from a lamp, or from thesun, and it falls on…
Astronomy · Telescopes
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