Page:The American Cyclopædia (1879) Volume VIII.djvu/41

 GLOBE may be approximately determined with- out 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 15th 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 Limburg, 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 56 ft. in diameter, and the delineations were upon the inside only. These were model- led 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 6,000 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 re- lief, and the surface painted in colors. A stair- way 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 manufac- ture, 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 H in. wide and 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 com- pass, commencing with the colures and eclip- tic. 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 foun- dation, 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 some- times requisite. When dry the paper covering is colored, and then sized with gelatine and immediately varnished. The final process be- fore mounting is to dry again at 200 F. Holtz- apftel 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 be brought under it. It is divided into de- grees, 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