Artificial Globe, a hollow sphere, on the surface of which is delineated a map of the earth or heavens, with the various circles to which points are referred to determine their positions. Globes are thus of two sorts, terrestrial and celestial. They serve as models to impart correct ideas of the form and movements of the earth and of the heavenly bodies, of their position in relation to each other at different times, of the relative positions of places upon the earth, and of the principle of designating these by lines of latitude and longitude. Globes are also applied to the mechanical solution of various astronomical problems, as the difference of time in different places, dependent on the position of the sun in relation to those places, the times of the rising and setting of the sun at any place, and many other similar questions, which may be approximately determined without recourse to mathematical calculations. But it is chiefly for the sake of the clear instruction in general geography, which many persons fail to derive from maps, that globes are especially valuable.

It is not known when they were first constructed; but the first celestial globe is supposed to have been made by Anaximander of Miletus, a pupil of Thales, who flourished in the 6th century B. C. Ptolemy made use of a terrestrial globe provided with the universal meridian, such as is applied to those now in use. Martin Behaim, the navigator, constructed a terrestrial globe at Nuremberg toward the close of the loth century. Tycho Brahe had one of copper nearly 5 ft. in diameter. Another was made in Venice in 1683 for Louis XIV., 12 ft. in diameter. Another, 11 ft. in diameter, constructed by Brousch of Lirnburg, attracted the attention of Peter the Great, who purchased it and removed it to St. Petersburg. It was large enough to accommodate 12 persons sitting around a table within it. Its inner surface was celestial, the stars being represented by gilded nails; and the outer surface was terrestrial. The national library of Paris has two globes of over 14 ft. diameter. A magnificent copper globe made for Louis XVI. is in the Mazarin library; and another of the same material and of admirable workmanship, designed by Poir-son for the instruction of the king of Rome, and bought by Louis XVIII. for 36,000 francs, belongs to the museum of the Louvre. In 1851 a large globe of novel construction was built in Leicester square, London, by Mr. Wyld. It was 50 ft. in diameter, and the delineations were upon the inside only.

These were modelled in slabs of plaster of Paris, which were set like a ceiling on the ribs of zinc which formed the framework of the structure. The slabs were cast in clay moulds, which were prepared with care from the most correct maps on a scale of 10 miles to the inch. About 0,000 slabs were required to cover the whole surface, their dimensions varying from two feet square as the width diminished toward the poles. The topographical features were represented in relief, and the surface painted in colors. A stairway wound around from the base, by which the circular platforms one above another were reached that brought the spectators near to the inner surface of the great shell. - The globes used by geographers in the middle of the last century were very similar to those now in use. Much attention was directed to their manufacture, and a treatise on their construction and use was published in 1769 by George Adams. The first requisite is a ball to receive the printed map; this is therefore first accurately measured, and due allowance is made for the shrinking each segment will experience after being wet. The diameter being determined, a silver-steel semicircle 1 1/2 in. wide and 1/4 in. thick is next made, of precisely half this diameter less that of the wires intended for the poles.

A globe of wood is now made three eighths of an inch less in diameter than the steel circle. Into two opposite points of this so-called mould bits of No. 7 wire are inserted for poles. Dry paper is laid all over it to prevent the pasted paper to be next laid from adhering. This is of coarse heavy quality, and eight or ten layers saturated with paste are applied in succession as evenly as possible, covering the whole surface. As this coating becomes dry, it shrinks and fits tightly over the mould. It is then hung by the poles in the front edge of a bench fitted to receive it, and by applying a knife on the line of the equator while the ball is made to revolve, the shell is cut through, so that it may be taken off the mould in two hemispheres. This being done, a turned stick of right length, with a short wire in each end for poles, is introduced, one end in each hemisphere, and the two shells being brought together are secured by glueing their edges. The ball, called in its present state the foundation, is placed in the steel semicircle, and coated with a composition of glue and whiting. Being made to revolve, the excess of the composition is removed by the circle, and the ball is thus turned smooth and true, after which it is carefully dried.

The next process is to lay out the lines of latitude and longitude, which is done by a beam compass, commencing with the colures and ecliptic. The first meridian is usually made to pass through the intersections of the equator and ecliptic, the points of the vernal and autumnal equinoxes; and from the former of these points the reckoning of the degrees on the equator and ecliptic begins. The maps are now to be cut on the engraved meridians of each 15°, thus making 24 segments; and these are pasted in succession with white paste upon the foundation, the lines drawn upon it serving as guides. The fitting requires great care, that the edges may be made to exactly coincide, and some stretching of the equatorial portions is sometimes requisite. When dry the paper covering is colored, and then sized with gelatine and immediately varnished. The final process before mounting is to dry again at 200° F. Holtz-apffel says : "A globe is usually covered with 26 pieces of paper, namely, 2 pole papers or circles, including 30° around each pole, and 24 gores meeting at the equator.

Sometimes the gores extend from the pole to the equator; every gore has then a narrow curved central notch extending 30° from the equator." The globe is hung for support by its poles in a brass circle, which goes round it and is called the universal meridian, inasmuch as any point upon the surface of the globe revolving in this may bo brought under it. It is divided into degrees, which on one side are reckoned from either pole toward the equator for the purpose of giving the elevation of the poles, and on the other from the equator toward either pole, to be used for finding the latitude of places. A frame or stand is prepared to receive the globe with its brass circle, the top presenting a broad horizontal circle with two vertical slots placed opposite each other for receiving the brass meridian, which when adjusted is free to slide around in its own plane, so that the poles may be upright, horizontal, or at any angle to the horizontal circle. Around this circle, which represents the rational horizon or imaginary plane passing through the centre of the earth, are drawn several concentric circles; the innermost represents the horizon, and the slots for the brass circle are on the N. and S. points; the degrees on the northern two quadrants are reckoned from E. and W. toward the N., and those on the southern toward the S. Outside of this is the circle representing the calendar, with the names of the months and divisions corresponding to the days.

The next circle contains the signs and degrees of the ecliptic, so arranged that against each day of the year is found the point of the ecliptic in which the sun is situated. In some globes the horizontal circle is made to revolve. It is attached to arms which extend below the brass meridian and unite, supporting the adjusting clamp which supports the brass meridian. A taper pin extends down three inches from the lowest part of the arms, and fits into a socket in the iron base, thus securing by the revolutions of the meridian and horizon in their own planes the effect of a universal joint, so that any part of the globe can be brought under observation without changing the position of the base. To the N. pole of the globe is attached a small circle of brass, called the hour circle, the pole passing through its centre, and holding it so that the two move round together, but yet permitting the hour circle to be moved round by the hand upon the axis. The circle is divided into 24 equal parts, corresponding to the hours of the day, and any one of these can be placed upon any meridian by turning the circle.

The quadrant of altitude is a brass slip equal in length to a quarter of the circumference, and divided into 90°. It is fastened to the brass meridian, and is used for measuring degrees in any direction on the globe. A mariner's compass is sometimes attached to the frame of the globe for the purpose of placing the meridian in a N. and S. line. The various circles connected with the terrestrial globe are equally appropriate to the celestial; and as the latter are ordinarily constructed, the observer is supposed to be looking down upon the heavens presenting a convex surface, upon which the stars and constellations are mapped in their proper relative positions. To render the nature of the imaginary circles to which the points upon both globes are referred more clear for the student, the armillary sphere was contrived, which consists of the several circles in the form of graduated brass rings placed in their appropriate positions, and containing in the centre a small globe representing the earth. These circles are the horizon, meridian, equator, ecliptic, equinoctial colure, and the solstitial colure.

The sphere formed by them is supported in a frame in the same manner as the globes. - Celestial and terrestrial globes are sometimes combined, the latter being enclosed in a glass sphere marked with the constellations. Globes are sometimes made also of India rubber or thin paper, and so contrived that they may be inflated with air. Some terrestrial globes contain, in addition to the usual geographical delineations, geological strata, atmospheric currents, isothermal lines, hydro-graphic information, and trade routes; and in some the land is represented in relief. Slate globes for school use are made with only the lines of latitude and longitude drawn on them; and wooden globes, painted black and similarly marked, are constructed, on which maps are drawn with chalk.