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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Armillary sphere | 2/5 | https://en.wikipedia.org/wiki/Armillary_sphere | reference | science, encyclopedia | 2026-05-05T09:40:04.003517+00:00 | kb-cron |
The globe assembly is supported on a pedestal N, and may be elevated or depressed upon the joint O, to any number of degrees from 0 to 90 by means of the arc P, which is fixed in the strong brass arm Q. The globe assembly slides in the upright piece R, in which is a screw at r, to fix it at any proper elevation. In the box T are two wheels (as in Dr Long's sphere) and two pinions, whose axes come out at V and U; either of which may be turned by the small winch W. When the winch is put upon the axis V, and turned backward, the terrestrial globe, with its horizon and celestial meridian, keep at rest; and the whole sphere of circles turns round from east, by south, to west, carrying the sun Y, and moon Z, round the same way, and causing them to rise above and set below the horizon. But when the winch is put upon the axis U, and turned forward, the sphere with the sun and moon keep at rest; and the earth, with its horizon and meridian, turn round from horizon to the sun and moon, to which these bodies came when the earth kept at rest, and they were carried round it; showing that they rise and set in the same points of the horizon, and at the same times in the hour circle, whether the motion be in the earth or in the heaven. If the earthly globe be turned, the hour-index goes round its hour-circle; but if the sphere be turned, the hour-circle goes round below the index. And so, by this construction, the machine is equally fitted to show either the real motion of the earth, or the apparent motion of the heavens. To reset the sphere for use, one must first slacken the screw r in the upright stem R, and taking hold of the arm Q, move it up or down until the given degree of latitude for any place lies at the side of the stem R; then the axis of the sphere will be properly elevated, so as to stand parallel to the axis of the terrestrial globe, if the globe assembly is to be aligned to north and south by a small compass: once this is done, the user must count the latitude from the north pole, upon the celestial meridian L, down towards the north notch of the horizon, and set the horizon to that latitude. The user then must turn the nut b until the sun Y comes to the given day of the year in the ecliptic, and the sun will be at its proper place for that day. To find the place of the moon's ascending node, and also the place of the moon, an ephemeris must be consulted to set them right accordingly. Lastly, the user must turn the winch W, until either the sun comes to the meridian L, or until the meridian comes to the sun (moving the sphere or globe at the user's discretion), and then set the hour-index to the XII, marked noon, the whole sphere will be reset. Then the user must turn the winch, and observe when the sun or moon rises and sets in the horizon. The hour-index will show the times thereof for the given day.
== History ==
=== China ===