GLOBE. 



the globe, and its base equal to the curve 

 superfices or the base of the sector, with 

 many other properties. And from hence 

 are easily deduced these practical rules 

 for the surfaces and solidities of globes 

 and their segments; viz. 1. "For the Sur- 

 face of a globe," multiply the square of 

 the diameter by 3.1416; or multiply the 

 diameter by the circumference. 2. " For 

 the Solidity of a Globe," multiply the 

 cube of the diameter by .5236 (viz. one- 

 sixth of 3.1416) ; or multiply the surface 

 by one-sixth of the diameter. 3. "For 

 the surface of a Segment," multiply the 

 diameter of the globe by the altitude of 

 the segment, and the product again by 

 3.1416. 4. "For the Solidity of a Segment,'* 

 multiply the square of the diameter of 

 the globe by the difference between three 

 times that diameter and twice the alti- 

 tude of the segment, and the pro- 

 duct again by .5236, or one-sixth of 

 3.1416. 



Hence, if d denote the diameter of the 

 globe, 



c the circumference, 



a the altitude of any segment, and 



p = 3.1416 ; then 



The surface. The solidity. 



In the globe. pd*=zcd^p& 



In the segment pad J pd 1 - X 3d2a 

 See MENSURATION. 



GLOBE, in practical mathematics, an 

 artificial spherical body, on the convex 

 surface of which are represented the 

 countries, seas, &.c. of our earth ; or the 

 face of the heavens, the circles of the 

 sphere, &c. That with the parts of the 

 earth delineated upon its surface is called 

 the terrestrial globe ; and that with the- 

 constellations, &c. the celestial globe. 

 These globes are placed in 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 

 and explain the phenomena arising from 

 the diurnal motion of the earth. 



The globes commonly used are com- 

 posed of plaister and paper in the follow- 

 ing manner : A wooden axis is provided, 

 somewhat less than the intended diame- 

 ter of the globe, and into the extremes 

 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 paste- 

 board 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 slip- 

 ped off the mould. They remain now to 

 be applied on the poles of the axis, as be- 

 fore they were on those of the mould ; 

 and to fix them in their new place, the 

 two edges are sowed 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 hasped in a metal- 

 line semi-circle of the size intended, and 

 a kind of plaster made of whiting, water, 

 and glue, heated, melted, and incorpo- 

 rated together, is daubed all over the pa- 

 per surface. In proportion as the plaster; 

 is applied, the ball is turned round in the 

 semi-circle, the edge of which 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 

 semi-circle, and fresh matier applied : 

 thus they continue alternately to apply 

 the composition, and dry it, till the ball 

 everywhere accurately touches. the semi- 

 circle ; in which state it is perfectly 

 smooth, regular, and complete. The 

 ball thus finished, it remains to paste the 

 map or description on it. In order to this, 

 the map is projected in several gores or 

 gussets, all which join accurately on the 

 spherical surface, and cover the whole 

 ball. To direct the application of these 

 gores, lines are drawn by a semi-circle 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. 



The papers thus pasted on, there re- 

 mains nothing but to colour and illumi- 

 nate the globe, and to varnish it, the bet- 

 ter to resist dust, moisture, &c. The 

 globe itself thus finished, they hang it iit 

 a brass-meridian, with an hour-circle and 

 a quadrant of altitude, and thus fit it into 

 a wooden horizon. 



There are ten principal circles repre- 

 sented upon globes, viz. six greater and 

 four lesser ones. The greater circles are 

 the horizon, meridian, and equinoctial, 

 as it is called on the celestial, and equator 

 on the terrestrial globe, the ecliptic 

 drawn along the middle of the zodiac, and 

 the two colures. 



