The page is enclosed in a decorative woodcut border featuring floral motifs and figures.

CHAPTER XIX

A square woodcut diagram shows a pair of drafting compasses measuring a curved line or arc, used here to illustrate the precision required in cartographic measurement.

We therefore undertake a double labor. First, that we might observe the opinion of the man referring to Marinus of Tyre throughout the entire composition, except in those instances where a certain correction is necessary. Second, that we might most conveniently reveal those things not made manifest by him, through more modern histories or a more accurate arrangement of tables, so that the description might attain its proper decorum. Furthermore, we have taken care to provide an easier method. For over all the provinces, we have diligently arranged individual, proper boundaries, showing what positions they hold according to both longitude and latitude. Additionally, we have included the mutual relationships of the most important peoples dwelling within them, as well as the exact distances of the most notable cities, rivers, gulfs, mountains, and other features that can be placed upon the map of the world. These distances are measured in parts, of which the great circle the Earth's circumference contains three hundred and sixty. For longitude, the meridian is described through the location starting from that which terminates the western end upon the equinoctial line. For latitude, the parallel is written through the same location from the equinoctial line upon the meridian. Thus, we will be able to immediately know the position of any place, as well as the relationships of the particular locations, the provinces to one another, and finally, the entire world.

CHAPTER XX

A square woodcut diagram displays a sphere or circle with intersecting lines and a V-shaped angle, illustrating the complexities of projecting spherical coordinates onto a flat plane.

However, each type of design has its own unique quality. For a description made upon a sphere preserves the likeness of the earth’s figure in itself and requires no other artifice for this work,

yet it does not easily provide a size capable of holding the many things that must necessarily be placed in their own locations. Nor can it adapt the description to the entire figure so that it may be seen in a single glance. Instead, one must transfer from one description to another; that is, either to the view or to the sphere. Neither of these happens with the description made on a plane, which seeks a certain mode similar to a spherical image so that it might make the distances that must be established within it as commensurable as possible. This should correspond to that appearance which aligns with the truth, which Marinus believed to be not at all a matter of chance. Nevertheless, he rejected all methods of planar descriptions, yet he himself seems to have used one that makes the distances the least commensurable of all. For instead of all the lines of circles, parallels, and meridians, he substituted straight lines. He also made the meridians equidistant from one another, similar to the parallels. He only observed the parallel that passes through Rhodes as being commensurable to the meridian, according to a ratio of nearly one and a quarter of the similar circumferences on a sphere—the ratio of the great circle to the parallel that is distant from the equinoctial line by thirty-six parts. He seems to have taken no care for the others, neither for the sake of symmetry nor for spherical representation. For when the view is first established toward the middle of the northern quadrant of the sphere, where the greatest part of the world is described, the meridians can provide an appearance of straight lines, since each one is set opposite to the revolution, and its plane falls through the vertex of the view. Truly, the parallels do not do so, on account of the distance of the northern pole. However, the segments of the circles manifestly show their convexities turned toward the south. Moreover, although in truth and in imagination these same meridians are similar, they nevertheless intercept unequal circumferences in parallels that differ in size, and they are always larger in those places that are closer to the equinoctial line. Marinus, however, makes them all equal. He extends the distances of the climates that are more northern than the parallel passing through Rhodes more than truth allows. Those that are more southern, he contracts, so that they no longer correspond to the number of stadia units of distance set by him, but they fall short under the equinoctial line by a fifth part, just as the parallel passing through Rhodes falls short of the equinoctial line. But the distances that are under the parallel that passes by...