Terrestrial and Celestial Globes Volume 2 / Their History and Construction Including a Consideration of their Value as Aids in the Study of Geography and Astronomy

by Edward Luther Stevenson

Fig. 136. Anonymous Globe Gores in Plane Map Construction, ca. 1550.

In referring to unusual forms in gore construction attention may again be called to the map of Alonso de Santa Cruz and to that of Antonius Florianus, in which maps the plan was hemispherical,[199] the central point in the construction of each hemisphere, a northern and a southern, being the pole, the circumference of the circle in which the thirty-six gores were drawn, representing the equator. But again we do not know that such a gore map was ever employed in globe construction though the method, it seems, would lend itself to that end.

It can be readily understood that numerous modifications in the matter of globe-gore construction and their application to the surface of the sphere, more or less detailed in character, were introduced as the years passed, but the modifications were by no means at all times in the line of improvement.[200] The technical skill of the present day does not surpass that which one occasionally finds exhibited in the work of some three hundred years ago.

In the matter of geographical record terrestrial globe maps stand with the plane maps of the same period. While they are by no means as numerous as the plane maps, there attaches to them an importance no less historically significant. Not infrequently they give us records not to be found elsewhere. In their general features, differences can hardly be said to exist between plane maps and globe maps. In the matter of adornment there is similarity; each following the practice of the time when constructed. As pictures and legends hold a place of prominence, particularly on mediaeval maps,[201] so even to the close of the period we have had under consideration, that is, the end of the eighteenth century, these adornments have place on globe maps, sometimes few, sometimes many, the same, if in picture, exhibiting the inhabitants of land and sea, if merely a legend, giving information of geographical importance on the terrestrial globe and of astronomical importance on the celestial, these legends being often placed in an artistic cartouch.

To the printed or engraved globe map, color was generally added by hand with an effect often very artistic, in contrast with which the modern machine methods of color printing are deplorably crude.

On most terrestrial globe maps meridian circles are represented at intervals of ten, twenty, or thirty degrees, the prime meridian on which the degrees of latitude are marked being usually made very conspicuous, and to the close of the period under consideration usually made to pass through the Cape Verde Islands or the Canaries, a point always to be carefully noted in attempting to get a reading for the longitude of any particular place. Parallels are usually drawn at intervals similar to those of meridians, the equator on which the degrees of longitude are marked, the tropics, and the polar circles being always conspicuous. The ecliptic or zodiac is usually indicated encircling the globe from the solstitial point on the tropics, intersecting the equator at the two opposite equinoctial points, through which as through the solstitial points the colures are made to pass.

Hues states that “Those lines which a ship, following the direction of the Magnetic Needle, describeth on the surface of the Sea, Petrus Nonius calleth in the Latin Rumbos, borrowing the appellation of his Countrymen the Portugals; which word, since it is now generally received by learned writers to express them by, we also will use the same,” that is, rhumbs or rhumb-lines.

These were represented on the globe, first by Mercator, by greater or lesser circles or “winding lines,” and were intended to be of aid to seamen in navigating from port to port across the great oceans. In their representation on the globe map cognizance was taken of the fact that all meridians of all places pass through both poles, crossing the equator therefore at right angles and all other circles parallel to it, and that if the navigator’s course is in any other direction than toward one of the poles he is continually changing his horizon and his meridian. The rhumbs as drawn were made to cut all meridians of all places at equal angles and to respect the same quarters of the world, that is, direction, whatever the horizon. Rhumbs can represent great circles only when they coincide with the equator or with any meridian.[202]

In the matter of draughting, printing, and mounting celestial globe gore maps the method employed may in general be said to be identical with that followed in terrestrial globe construction. It should, however, be noted that in pasting the gores on the surface of the sphere they were often so applied as to have their points or angles meet at the pole of the ecliptic, in what may be called the ecliptic system, instead of applying them to meet at the poles of the equator, the globe itself being generally so mounted as to revolve in the equatorial system, its poles of revolution being attached to the meridian circle.[203]

The figures of the several constellations were usually drawn with care, occasionally with high artistic taste, as those drawn by Hevelius (Fig. [137]) and copied by Gerhard and Leonhard Valk for their celestial globes (Fig. [138]). The several stars represented on the map, the majority of them being either lettered or named, were usually from the first to the sixth magnitude, each represented in its proportional size, while an explanatory table for the several magnitudes was usually given on some one of the gores. The stars and the figures of the several constellations, let it be noted, were not made to appear on the surface of the sphere, with rare exceptions, in their relative location as they appear to the observer who beholds them from his position on the surface of the earth, but are reversed. To the astronomer the earth is but a point in space, to the layman, so far as mere appearance is concerned, it is the center about which the starry heavens appear to revolve. With the pole (north for us in the northern hemisphere) as the center of the dial face the stars appear to move in a direction the reverse of that in which the hands of a clock are made to move. The astronomer, that is, the celestial globe maker, thinks of himself as placed beyond the vaulted heavens in which the stars appear to be located, and as looking down upon this vaulted dome as on the surface of his celestial globe. An illustration may here well serve us. As one observes serves Ursa Major on any starry night, which constellation we commonly call the Great Dipper, the bowl of the dipper, which is located in the body and flank of the bear, leads in its apparent motion around the pole star, being followed by the handle of the dipper or the tail of the bear (Fig. [139]). On the surface of the celestial sphere, however, the position of bowl and handle was usually reversed, the constellation appearing as it would to the beholder who finds himself beyond the stars. Naturally the planets could not be represented on the surface of a solid celestial sphere; only in the armillary sphere or the orrery could they find place. In these instruments we generally find them represented, each with its circle or orbit properly given, and relatively properly placed.