A complete globe was further furnished with a quadrant of alt.i.tude, ninety degrees in length, this being attached at one end to the meridian circle, yet movable to any degree of the meridian, though commonly set at the zenith. This quadrant served for measuring alt.i.tudes or for finding amplitudes or azimuths.

The small hour circle,[207] fitted to the meridian, its center being the pole and for us the north, was marked with the twenty-four hours of the day, each hour being again divided into halves and quarters. An index attached to the axis of the globe pointed out successively the hours as the globe was revolved. The use of this hour circle was to indicate the time of the successive mutations, including the rising and the setting of the celestial bodies and the time of their pa.s.sing successively the meridians.

As a compa.s.s was often set into the horizon circle so also we frequently find a large or small compa.s.s set into that plate which in certain globes was employed as a support, tying together, as it were, the lower extremities of the base columns.[208]

It will have been noted that the globes referred to in the preceding pages varied greatly as to size, from the small ball representing the earth, and but a few centimeters in diameter, to be found in the center of those armillary spheres representing the Ptolemaic geocentric system, to the great globe of Coronelli fifteen feet in diameter constructed for Louis XIV of France. With rare exceptions metal globes were made small in size. Those globe b.a.l.l.s or spheres, in the construction of which a mould was employed, usually had a diameter under 50 cm., although we find some of them twice this size. Such spheres had the advantage of lightness though often were frail in structure and liable to lose their perfect sphericity.

[Ill.u.s.tration: Fig. 140. Terrestrial Globe Gores by Johannes Oterschaden, ca. 1675.]

In the matter of special ornamentation or decoration, to be observed in globe mountings, individual taste was given unlimited freedom to express itself, and in certain instances it will have been noted that these mountings were exceedingly elaborate.

Primarily we may say that globes were constructed for the useful purpose of promoting geographical and astronomical studies, generally recording the latest and best geographical or astronomical information and in form superior to that which could be set down on the plane map, but they also had a place of importance, secondary we may call it, on account of their decorative value. They came to be considered almost essential as adornments for the libraries of princes, of prosperous patricians, and of plodding students, and their mountings were often especially fashioned for the places they were to occupy. They seemed to lend an air of scholarly respectability; to suggest that their possessors wished to pay, certainly a modic.u.m of homage to the sciences which globes were calculated to promote.

A brief concluding word may well be added touching those globes which may of course be cla.s.sed as celestial, but which are known as moon globes and planetariums or orreries. There could be no practical value in an attempt to set forth a map of the surface of the stars, nor of the planets while our knowledge is so limited, although Schiaparelli has undertaken, with measurable success, to map the surface of Mars,[209]

and it would be next in order to construct a Mars globe. Of the surface of our moon much is known and maps of it have been constructed, as indeed have been moon globes. We are informed that about the middle of the seventeenth century the Danish astronomer, Hevelius, who designed so successfully star maps, entertained the idea of constructing a moon globe,[210] but we do not know that he set his hand to the work. A century later it appears that the French astronomer La Hire actually completed a moon globe,[211] but it has been possible to obtain only the briefest reference to it.

Tobias Mayer of Nurnberg, a contemporary of La Hire, set himself to the draughting of gore maps[212] intended for use in the manufacture of moon globes. Mayer found employment in the Homann establishment of Nurnberg, being regarded as an exceedingly skilful draughtsman, able to sketch on his draughting sheet that which he saw through his telescope.

His plan contemplated the making of twelve gores or segments, six for the northern half of the moon and six for the southern. His plan, of course, would enable him to represent but one side of the moon,--that turned toward the earth,--although it appeared that he contemplated the addition of two segments on which, in at least a fragmentary manner, he was to represent what we may call the border of the opposite side of the moon. Mayer seems not to have completed his work, since we find nowhere an example of his finished product.

It was not until near the close of the eighteenth that we again meet with an attempt to construct a moon globe and it seems that the task was accomplished by the Englishman, John Russel. It was in the year 1796 that he proposed to raise by subscription the necessary funds for making his undertaking a success. His globe has a diameter of 12 inches,[213]

and was furnished with the necessary adjustable shield that the moon's waxing and waning could be represented. That this moon globe was actually constructed, although no copy has been located, we are informed by Wolf. Such attempts as were made in the nineteenth century with a good measure of success do not here call for consideration.

It has been previously noted that the so-called globe of Archimedes may have been a sort of planetarium, and that during the middle ages such instruments were constructed and employed in astronomical instruction.

None, however, have come down to us out of those early years.

Astronomers of the seventeenth and eighteenth centuries, as we know, made frequent use of planetariums, such for example as were constructed by the Dutch astronomer, Christiaan Haygens (1629-1695) for the ill.u.s.tration of planetary motion according to the Copernican system.

Each of the planets was represented in his machine by a small ball, attached to an arm, which could be made to move through an orbit around the sun. In the more complicated machines the several planetary moons, such as the moons of Jupiter, were represented and were made to perform their proper motions.

[Ill.u.s.tration: Fig. 141. Celestial Globe Gores by Johannes Oterschaden, ca. 1675.]

[Ill.u.s.tration: Fig. 142. Engraved Sections for Globe Horizon Circle by Johannes Oterschaden, ca. 1675.]

In the eighteenth century the instrument maker, George Graham (1675-1751), constructed a complicated planetarium, in honor of Charles Boyle, Earl of Orrery (1676-1731), which he called an orrery. His machines, varying much in the character of construction, were especially popular in the eighteenth century. The nineteenth century saw them frequently in use for purposes of instruction and the regret may well be expressed that for serious purposes they seem to have lost favor.

[Ill.u.s.tration: Fig. 143. The Orrery.]

NOTES

[181] See Fig. 56, I, 116.

[182] Compare for example Figs. 8 and 89.

[183] Consult the 'Fihrist' referred to in Chap. III, n. 4.

[184] Note such examples as the globe of Robertus de Bailly, I, 108, the Lenox globe, I, 72, the Nancy globe, I, 102, and the Morgan globe in the Metropolitan Museum, I, 200.

[185] See Fig. 3.

[186] See Fig. 43.

[187] See Apia.n.u.s' Cosmographicus liber.

[188] As for example the World map of Mercator of the year 1538, an original copy of which may be found in the New York Public Library, also a copy in the Library of The American Geographical Society.

[189] D'Avezac, M. A. P. Coup d'oeil historique sur la projection des cartes de geographie. (In: Bulletin de la Societe de Geographie de Paris. Paris, 1863, pp. 274 ff.); Breusing, A. Das Verebnen der Kugeloberflache. Leipzig, 1892; Zondervan, H. Allgemeine Kartenkunde. Leipzig, 1891; Fiorini, M. Le projezioni delle carte geografiche. Bologna, 1881. The literature relative to map projection is very extensive.

[190] Fiorini. Sfere terrestri e celesti. pp. 93-102.

[191] See Fig. 32.

[192] See Fig. 40.

[193] Durer, A. Underweysung der Mesung mit dem Zirkel und Richtscheyd, in Linien ebnen und ganzen Corporen. Nurnberg, 1525.

[194] Buchlein, pp. 5 ff.

[195] Consult Gunther. Erd- und Himmelsgloben. pp. 72-73; Kastner.

Geschichte der Mathematik. Vol. I, p. 684. See Gunther, op. cit., chaps, vii, x, xii, xiii, xiv, with numerous references.

[196] Henrici Glareani poetae laureati de geographia liber unus.

Basileae, 1527.

[197] There is an interesting bit of information given by Coronelli in his 'Epitome Cosmografica' relative to the making of an adhesive material for use in the mounting of globe maps.

[198] See Fig. 61.

[199] See Figs. 59 and 66.

[200] Such, for example, as might consist of zonal strips, one for the torrid, one for each of the temperate, and one for each of the polar zones. Such strips perhaps could not properly be termed gores.

[201] Pictures are a particularly striking feature of the cloister maps of the middle ages. The idea of such adornments may have come down from Greek or Roman days. Plutarch tells us in his 'Theseus'

that "Geographers crowd into the edge of their maps parts of the world about which they have no knowledge, adding notes in the margins to the effect that only deserts full of wild beasts and impa.s.sable marshes lie beyond." Jonathan Swift, humorously referring to maps of the early period, writes:

"So geographers in Afric maps With savage pictures fill their gaps And o'er unhabitable downs Place elephants for want of towns."

The early map makers as ill.u.s.trators should be an interesting theme for a special monograph.

[202] Nonius, P. De arte atque ratione navigandi. Conimbriae, 1573, lib. II, c. xxi, xxiv; Hues. Tractatus de Globis (Hakluyt Soc.

Pub.). pp. 127-147.

[203] For ill.u.s.tration of the method, see Fig. 89.

[204] Burritt, L. H. The geography of the heavens. New York, 1833; Allen, R. H. Star names and their meanings; Wolf. Geschichte der Astronomie. pp. 188-191, 420-427; Olcott, W. T. Starlore of all ages. New York, 1911.

[205] The literature relating to this particular branch of astronomy is extensive. Wolf, loc. cit., with references.

[206] See especially Fig. 13.