Terrestrial & Celestial Globes. Edward Luther Stevenson. Читать онлайн. Newlib. NEWLIB.NET

Автор: Edward Luther Stevenson
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Жанр произведения: Математика
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who have carefully considered these things, have decided that there is nothing more suitable than wood and for the following reasons. If the globe should be made of gold, only a very rich man would be able to possess it; furthermore it would be very heavy. If it should be made of thin sheets of gold it could be easily indented and would not long remain a perfect sphere. If it should be made small, that which was represented thereon would not appear distinct. The same thing may be said of silver, although it is a metal stronger than gold, as it is likewise harder, and therefore is not so easily indented. Copper is a metal harder than either silver or gold, but is so dry that it can not be easily fashioned into a globe, which should always be well made. Brass, which is like dark colored copper, may be more easily fashioned, because it is more malleable than copper, and is stronger than either gold or silver. If, however, a globe made of this material should be thin it might easily lose its shape, and if thick it would be very heavy. Of all metals, however, this is the one most suitable for use in making spheres, as it is the one most commonly employed. A globe of iron would be very difficult to make and would be very heavy, and since the rust would have to be removed from it very frequently, there would be much danger of destroying the figures. A globe of tin, if made of a thin sheet, could be easily indented, and would be very heavy if the sheet of which made were thick. Lead, if thin, would offer less resistance to injury than tin, and is a material much heavier. Furthermore, as lead is inclined to turn black, the figures and the stars represented on a globe of this material would soon become so discolored as to be no longer visible. There is no way by which it can be cleaned without wiping out the figures. Although the metal could be combined to form that material of which water jugs and buckets are made it would be so fragile as to break like glass. Clay, which is also used for the making of water jugs, mortars, and fountains, is not suitable for globes, because if thin it would break easily, and if thick it would be very heavy. Moreover this material when prepared must be baked in a kiln which fact renders it unsuitable for use in making spheres. A globe should not be made of stone, since if this were transparent the figures could not easily be seen, and such material would be very heavy. It would not be fitting to make so noble an object as a sphere of the material of which jars are made. Leather would not be suitable, though it might be fashioned into a permanent spherical shape. Such material shrinks in hot weather or when brought near a fire. Cloth would not be suitable, though it were made very strong, since heat would cause it to shrink, and moisture would cause it to lose its shape, and this same thing may be said of parchment. A sphere of wood is strong and is of reasonable weight and may be made in the manner which we shall set forth.” The original manuscript of this work is profusely illustrated, including representations of the figures of the several constellations (Fig. 20).

      Fig. 20. The Constellation Taurus.

      There appears to be only the slightest evidence that Campano was acquainted with the work of Alfonso. His presentation of the subject, in all probability, was altogether independent of a knowledge of the Alfonsian tables. It is interesting to observe that in the day when astrology was in great favor in the universities of Europe, Campano continued to be interested in genuine astronomical science.

      The increasing interest in geography and in astronomy in the closing years of the middle ages led most naturally, in time, to much activity in globe construction, and to this fact attention is directed in the following chapter.

       NOTES

      70 Beazley’s monumental work, previously cited, considers the geographical knowledge of the Christian middle ages, from the closing years of the Western Roman Empire to the early years of the fifteenth century. See especially Vol. I, chap. vi; Vol. II, chap. vi; Vol. III, chap. vi. Marinelli, G. Die Erdkunde bei den Kirchvätern. Leipzig, 1884; Kretschmer, K. Die physische Erdkunde im christlichen Mittelalter. Wien, 1889; Cosmas Indicopleustes. Christian Topography, tr. by J. M. McCrindle. (In: Hakluyt Society Publications. London, 1897); Günther, S. Die kosmographischen Anschauung des Mittelalters. (In: Deutsch. Rundschau für Geographie und Statistik. Vol. IV, pp. 135 ff.)