The Geography

...drawing them among themselves in the manner of straight parallels. He preserved only the parallel of Rhodes The line of latitude passing through the island of Rhodes, calculated by ancient geographers to be at 36 degrees north as commensurable with the meridian A line of longitude, according to the ratio of roughly five-fourths original: "epitecarti." A mathematical ratio of 5:4 (or 1.25), used here to describe the proportion between a degree of latitude and a degree of longitude at the latitude of Rhodes of the similar arcs of the great circle of the sphere to the parallel distant from the equinoctial The Equator by thirty-six degrees. Of the others, however, he took no care, neither concerning the proportion of dimensions nor the spherical appearance.

For first, if the eye is positioned in the middle of the northern fourth part of the sphere, in which most of the habitable part of the earth is described, the meridians can indeed give the appearance of straight lines, since as they revolve, any of them may be positioned directly opposite us, so that its plane passes through the eye and the point directly overhead. This does not happen for the parallels, however, because of the elevation of the North Pole; instead, the sections of the circles clearly show curvatures turning toward the meridian.

Furthermore, regarding both truth and appearance, although the same meridians intercept similar but unequal arcs on parallels of different sizes—and these arcs are always larger the closer they approach the equinoctial—Marinus makes them all equal. He extends the spaces of the more northern regions beyond the truth compared to the parallel through Rhodes, and he diminishes those that are further south more than is right. From this, it follows that the distances of places can by no means be adapted to the measurements of stadia An ancient unit of distance, roughly 185 meters set forth by him, but those under the equinoctial are deficient by a full fifth part—the amount by which the parallel through Rhodes is smaller than the equinoctial. Conversely, he increases the distances under the parallel through Thule original: "tyle." A semi-mythical land considered the northernmost point of the known world by four-fifths; for the parallel through Rhodes is nearly four times a fifth part larger than the parallel through Thule.

For almost any circle described at thirty-six degrees from the equinoctial (the parallel of Rhodes) consists of ninety-three such parts where the equinoctial degrees are one hundred and fifteen. Truly, the circle which is sixty-three degrees from that same equinoctial (the parallel through Thule) consists of fifty-two parts.

C ### What must be observed for the drawing of the world on a plane.

THEREFORE, it will be well done to keep the lines that are placed for the meridians straight, but those that will be marked for the parallels should be drawn as arcs of circles having one and the same center. From this center, as if from the North Pole, the straight lines of the meridians are to be drawn, so that in other respects the likeness of the form and appearance of the spherical surface may be preserved.

Then, while the meridians remain without deviation toward the parallels and also emerge from the same common pole, since it is not possible to preserve the proportion found on the sphere through all the parallels, it will be sufficient to maintain it at the parallel through Thule and at the equinoctial, so that the sides which encompass the latitude are made equal to the true and natural sides of the earth.

It will be necessary to mark the parallel through Rhodes, in which most proofs of the distances of longitude have been made, according to the predicted proportion just as Marinus reported; that is, according to the five-fourths ratio of the circumference of the great circle to it, so that the longitude of our habitable world original: "habitabilis." The "Oikoumene," or the known inhabited world (which is better known than its latitude) may be commensurable. In what form and manner these things will be treated will be manifest hereafter, just as we shall set forth the description of the work itself as is required.

C ### How our habitable world should be marked on a sphere.

THE size of this [globe] can be determined by the intention of the maker according to the number of places to be marked, as ease and ambition suggest. For the larger it is constructed, the more copious and elevated the description of places will be. However large it may be, once the poles of that sphere are established, we shall carefully suspend a semicircle from them, very slightly distant from the spherical surface so that in its rotation no friction occurs. This semicircle should be narrow so that it does not occupy many places across the latitude, and it should have another...