GLOBE, is more particularly used for an artificial sphere of metal, plaster, paper, or other matter; on whose convex surface is drawn a map, or representation, either of the earth, or heavens, with the several circles conceived thereon. See GEOGRAPHY.
Globes are of two kinds, terrestrial and celestial; each of very considerable use, the one in astronomy, and the other in geography; to perform many of the operations thereof, in an easy, sensible manner, so as to be conceived without any knowledge of the mathematical grounds of those arts.
The fundamental parts, common to both globes, are an axis, representing that of the world; and a spherical shell, or cover, which makes the body of the globe, on whose external surface the representation is drawn. See AXIS, POLE, &c.
Globes, we have observed, are made of divers materials, viz. silver, brass, paper, plaster, &c. Those commonly used, are of plaster, and paper: The construction whereof is as follows:
Construction of GLOBES.—A wooden axis is provided, somewhat less than the intended diameter of the globe; and into the extremes hereof two iron wires are driven, for poles: this axis is to be the beam, or basis of the whole structure.
On the axis are applied two spherical, or rather hemispherical caps, formed on a kind of wooden mould or block.—These caps consist of pasteboard, or paper, laid one lay after another, on the mould, to the thickness of a crown-piece; after which, having stood to dry and embody, making an incision along the middle, the two caps thus parted are slipped off the mould.
They remain now to be applied on the poles of the axis, as before they were on those of the mould: and to fix them in their new place, the two edges are sewed together with pack-thread, &c.
The rudiments of the globe thus laid, they proceed to strengthen and make it smooth and regular. In order to this, the two poles are fastened in a metalline semicircle, of the size intended; and a kind of plaster, made of whiting, water, and glue, heated, melted, and incorporated together, is daubed all over the paper-surface. In proportion as the plaster is applied, the ball is turned round in the semicircle, the edge whereof pares off whatever is superfluous and beyond the due dimension, leaving the rest adhering in places that are short of it. After such application of plaster, the ball stands to dry; which done, it is put again in the semicircle, and fresh matter applied: thus they continue alternately to apply the composition, and dry it, till such time as the ball every where accurately touches the semicircle; in which state it is perfectly smooth, regular, firm, &c.
The ball thus finished, it remains to paste the map or description thereon: in order to this, the map is projected in several gores, or gaskets; all which join accurately on the spherical surface, and cover the whole
Globularia 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 those of the gores, and subdividing those again answerably to the lines and divisions of the gores.
Glocester. The papers thus passed on, there remains nothing but to colour and illuminate the globe; and to varnish it, the better to resist dust, moisture, &c.—The globe itself thus finished, they hang it in a brass meridian, with an hour-circle, and a quadrant of altitude; and thus fit it into a wooden horizon.
For the uses, &c. of the globes, see GEOGRAPHY, n° 33. 35, &c. ASTRONOMY, n° 168, 320. and Plate XLVIII. fig. 2.