Herschel, John F. W. (John Frederick William), Sir, 1792-1871 · London : Longman, Rees Orme · leaf 89
raduation ofcircles, but by the help of the earths diurnal motion,which carries equal arcs of the equinoctial across themeridian, in equal times, at the rate of 15° per siderealhour. In all other cases, when we would measureangular intervals, it is necessary to have recourse to cir-cles, or… … (numbered in order from any point 0° in the circum-ference, round to the same point again,) and connectedwith its centre by spokes or rays, x y z, firmlyunited to its circumference or limb. At the centrelet a circular hole be pierced, in which shall move apivot exactly fitting it, carrying a tube,…
Astronomy
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