Lockyer, Norman, Sir, 1836-1920, Seabroke, G. M. (George Mitchell), 1848-1918 · London, Macmillan and co. · leaf 44
it was employed as follows :— The circle A was fixed perfectly upright in the1 28,279 miles. CHAP. II.] THE FIRST INSTRUMENTS. 21 meridian, so that the greatest altitude of the sun eachday could be observed; the circle B was then placedexactly in the plane of the earths equator by adjustingthe line… … Fig. 7.—The First Instrument Graduated into 360° (West Side). circle E must fall upon the part marked f, so as exactlyto cover it. We now come to the time when the circle began tobe divided into 360 divisions or descrees—about thetime of Hipparchus (160 B.C.). There are twoinstruments described by…
Astronomy · Telescopes
Internet Archive · Wellesley College Library · Public Domain Mark 1.0. Free to use for anything.
