Herschel, John F. W. (John Frederick William), Sir, 1792-1871 · London : Longman, Rees Orme · leaf 91
to point out and read off the exact division of the circleat B, the point close to it. It is evident that, as thetelescope and circle revolve through any angle, the partof the limb of the latter, which by such revolution iscarried past the index F, will measure the angle de-scribed. This is the… … lastly, a compound microscope {fig* c), represented insection (in fig. d), and furnished with a cress in thecommon focus of its object and eye-glass, moveable bya fine-threaded screw, by which the intersection of thecross may be brought to exact coincidence with theimage of the nearest of the…
Astronomy
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