in geometry, a round or spherical body more usually called a sphere. See Sphere.

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, for performing many of the operations thereof in an easy obvious 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 the external surface of which the representation is drawn. See Axis, Pole, &c.

Globes, we have observed, are made of different 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 halved in a metallic semicircle of the size intended; and a kind of plaster, made of whitening, 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 parts 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 everywhere 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 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 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.

The papers thus pasted 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 wood horizon.

To describe the gores, or gussets, for the globes. In Chambers's Dictionary, the following method is directed.

1. From the given diameter of the globe, find a plate right line AB, fig. 1, equal to the circumference of a CCXXI. great circle, and divide it into twelve equal parts.

2. Through the several points of division, 1, 2, 3, 4, &c. with the interval of ten of them, describe arches mutually intersecting each other in D and E; these figures or pieces duly pasted or joined together will make the whole surface of the globe.

3. Divide each part of the right line AB into 30 equal parts, so that the whole line AB, representing the periphery of the equator, may be divided into 360 degrees.

4. From the poles D and E, fig. 2, with the interval of 23½ deg. describe arches a b; these will be twelfth-parts of the polar circles.

5. After the like manner, from the same poles D and E, with the interval of 66½ deg. reckoned from the equator, describe arches c d; these will be twelfth-parts of the tropics.

6. Through the degree of the equator ε, corresponding to the right ascension of any given star, and the poles D and E, draw an arch of a circle; and taking in the compasses the complement of the declination from the pole D, describe an arch intersecting it in i; this point i will be the place of that star.

7. All the stars of a constellation being thus laid down, the figure of the constellation is to be drawn according to Bayer, Hevelius, or Flamsteed.

8. Lastly, after the same manner are the declinations and right ascensions of each degree of the ecliptic d g to be determined.

9. The surface of the globe thus projected on a plane is to be engraved on copper, to save the trouble of doing this over again for each globe.

10. A ball, in the mean time, is to be prepared of paper, plaster, &c. as before directed, and of the intended diameter of the globe; on this, by means of a semicircle and style, is the equator to be drawn; and through every 30th degree a meridian. The ball thus divided into twelve parts, corresponding to the segments before projected, the latter are to be cut from the printed paper, and pasted on the ball.

11. Nothing now remains but to hang the globe as before in a brass meridian and wooden horizon; to which may be added a quadrant of altitude made of brass, and divided in the same manner as the ecliptic and equator.

If the declinations and right ascensions of the stars be not given, but the longitudes and latitudes in lieu thereof, the surface of the globe is to be projected after the same manner as before; except that, in this case, Globe. case, D and E, fig. 2, are the poles of the ecliptic, and f b the ecliptic itself; and that the polar circles and tropics, with the equator g d, and the parallels thereof, are to be determined from their declinations.

M De La Lande, in his Astronomie 1771, Tom. 3, p. 736, relates the following methods. "To construct celestial and terrestrial globes, gores must be engraved, which are a kind of projection, or inclosure of the globe (fig. 3,) similar to what is now to be explained. The length PC of the axis of this curve is equal to a quarter of the circumference of the globe; the intervals of the parallels on the axis PC are all equal, the radii of the circles KDI which represent the parallels are equal to the cotangents of the latitudes, and the arches of each, as DI, are nearly equal to the number of the degrees of the breadth of the gore (which is usually 30°) multiplied by the sine of the latitude; thus, there will be found no intricacy in tracing them; but the difficulty proceeds from the variation found in the trial of the gores when pasting them on the globe, and of the quantity that must be taken from the paper, less on the sides than in the middle; (because the sides are longer) to apply it exactly to the space that it should cover.

"The method used among workmen to delineate the gores, and which is described by Mr Bion (Ufage des Globes, Tome 3,) and by Mr Robert de Vaugendy in the 7th volume of the Encyclopédie is little geometrical, but yet is sufficient in practice. Draw on the paper a line AC, equal to the chord of 15°, to make the half breadth of the gore; and a perpendicular PC, equal to three times the chord of 30°, to make the half length: for these papers, the dimensions of which will be equal to the chords, become equal to the arcs themselves when they are pasted on the globe. Divide the height CP into 9 parts, if the parallels are to be drawn in every 10°; divide also the quadrant BE into 9 equal parts through each division point of the quadrant as G; and through the corresponding point D of the right line CP draw the perpendiculars HGF and DF, the meeting of which in F gives one of the points of the curve BEP, which will terminate the circumference of the gore. When a sufficient number of points are thus found, trace the outline PIB with a curved rule. By this construction are given the gore breadths, which are on the globe, in the ratio of the cosines of the latitudes; supposing these breadths taken perpendicular to CD, which is not very exact, but it is impossible to prescribe a rigid operation sufficient to make a plane which shall cover a curved surface, and that on a right line AB shall make lines PA, PC, PB, equal among themselves, as they ought to be on the globe. To describe the circle KDI which is at 30° from the equator; there must be taken above D a point which shall be distant from it the value of the tangent of 60°, taken out either from the tables, or on a circle equal to the circumference of the globe to be traced; this point will serve as a centre for the parallel DI, which should pass through the point D, for it is supposed equal to that of a cone circumscribing the globe, and which would touch at the point D.

"The meridians may be traced to every 10 degrees, by dividing each parallel, as KI, into three parts at the points L and M, and drawing from the pole P, through all these division points, curves, which represent the intermediate meridians between PA and PB; (as BR and ST, fig. 4.) The ecliptic AQ may be described by means of the known declination from different points of the equator that may be found in a table; for 10°, it is 3° 58′; for 20°, 7° 50′ = BQ; for 30°, 11° 29′, &c."

It is observed in general, that the paper on which charts are printed, such as the colombier, shortens itself ⅓ part or a line in six inches upon an average, when it is dried after printing; this inconvenience must therefore be corrected in the engraving of the gores: if notwithstanding that, the gores are found too short, it must be remedied by taking from the surface of the ball a little of the white with which it is covered; thereby making the dimensions suitable to the gore as it was printed. But what is singular is, that in drawing the gore, moistened with the paste to apply on the globe, the axis GH lengthens, and the side AK shortens, in such a manner, that neither the length of the side ACK nor that of the axis GEH of the gore are exactly equal to the quarter of the circumference of the globe, when compared to the figure on the copper, or to the numbered sides shown in fig. 4. Mr Bonne having made several experiments on the dimensions that gores take after they had been parted ready to apply to the globe, and particularly with the paper named jefus that he made use of for a globe of one foot in diameter, found that it was necessary to give to the gores, on the copper, the dimensions shown in fig. 4. Supposing that the radius of the globe contained 720 parts, the half breadth of the gore is AG = 188½, the distance AC for the parallel of 10 degrees taken on the right line LM is 128¼, the small deviation from the parallel of 10 degrees in the middle of the gore ED is 4, the line ABN is right, the radius of the parallel of 10° or of the circle CEF is 408¾, and so of the others as marked in the figure. The small circular cap which is placed under H, has its radius 253 instead of 247, which it would have if the fine of 20° had been the radius of it.

For the uses, &c. of the globes, see Geography and Astronomy, with the Plates there referred to.

Globe-Animal. See Animalcule, no. 29.

Globe-Fish. See Ostracion.