Globe, or Sphere, in Geometry, a solid figure described by the revolution of a semicircle round its diameter, which remains unmoved; or it may be defined as a solid, bounded by a uniform convex surface, which is in every part equally distant from a point called the centre.
Globe, in Practical Mathematics, an artificial sphere, on which are represented the countries and seas of our earth, or the face of the heavens, the circles of the sphere, etc. That with the parts of the earth delineated upon it is called the "Terrestrial Globe," and that with the constellations of the heavens, the "Celestial Globe." These globes are mounted on frames with other appurtenances. Their principal use, besides serving as maps to distinguish the outward parts of the earth, and the situation of the fixed stars, is to illustrate the various phenomena arising out of the diurnal motion of the earth. The globes commonly used are constructed of plaster and paper in the following manner: a wooden axis is provided somewhat less than the intended diameter of the globe, and into the extremities iron wires are driven for poles; on this axis are applied two hemispherical caps, formed on a spherical wooden mould by pasting several sheets of paper on the mould one over the other to about the thickness of a crown piece, and cutting them through the middle when they are dried, and slipping them off the mould. They are now applied to the poles of the axis, and the two edges are sewed together with packthread.
The rudiments of the globe thus laid, they proceed to strengthen it and make it regular. In order to do this the two poles are hasped in a metallic semicircle of the size intended, and a plaster made of whiting, water, and glue, well incorporated together, is daubed all over the surface; in proportion as the plaster is applied, the ball is turned round in the semicircle, the edge of which pares off whatever is superfluous, and beyond the due dimensions, leaving the rest adhering in places that are short of it; the ball is then set to dry, after which it is again set in the semicircle, and fresh plaster applied; and thus they continue to apply fresh composition, and to dry it, till the ball every where accurately touches the semicircle, in which state it is perfectly smooth and regular. The next thing is to paste the map on it: in order to this the map is projected in several gores or gussets, all of which join accurately on the surface, and cover the whole ball. To direct the application of these gores, lines are drawn by a semicircle on the surface of the ball, dividing it into a number of equal parts, corresponding to the number of gores, and subdividing those again answerably to those of the gores.
The paper thus pasted on, there remains nothing but to colour and illuminate the globe, and to varnish it, the better to resist dirt and moisture. The globe itself thus finished, is suspended in a brass meridian with an hour circle and a quadrant of altitude, and then fitted into a wooden horizon, which is supported by the legs of the frame.
Major Muller, G.L. has contrived a new arrangement of the globes, to which he has given the name of the cosmophere, and which forms the subject of the annexed engraving. The celestial globe consists of a hollow glass sphere, on which are depicted the stars constituting the various constellations. This sphere is furnished with brass circles, representing the equinoctial, the ecliptic, the colures, and the polar circles. The glass sphere separates at the equinoctial into two hemispheres, for the purpose of admitting within it a terrestrial globe, which is manufactured in the usual way: this globe is also furnished with brass circles, which are adjustable, to represent at pleasure the meridian and the horizon of any assigned place. The axis of the globe passes through the sphere, and supports both in a strong brass ring, which may be either attached to a stand, and made to rest upon a table, or suspended from the ceiling of a room, with a counterpoise w, as represented in the engraving, which will render the construction clear when compared with the following references, a a represents the equinoctials, where the two hemispherical glasses g g are united, and from which the declination of the stars is to be measured; c represents one of the colures, and f one of the terrestrial meridians; h one of the polar circles, and m m the large brass circle or general meridian, in which the apparatus is suspended by the poles N and S.
By the cosmosphere, as we have described it, the position of the earth, with respect to the fixed stars, may be shown at any given time; and by placing on the celestial sphere patches to represent portions of the sun, moon, and planets, the position of the earth with respect to these bodies may also be represented with facility; hence many of the astronomical phenomena arising from the position of the earth, with regard to the other bodies, can be familiarly illustrated, and numerous useful problems readily solved. But to extend its usefulness, the patentee has made arrangements for removing the globe from the interior of the system, and placing in its stead the sun and planetary system; and by this means the relative positions of the planetary bodies may be interestingly represented. He has likewise pro-vided brass graduated circles, by which, when they are attached to the celestial sphere, the nature of the various astronomical and nautical problems depending upon spherical trigonometry may be pleasingly explained.