On Terrestrial Longitude.

CHAPTER VII.

Decorative initial letter L featuring a satyr-like figure.
The longitude of a place (as Werner alludes) is a segment of the equator or equinoctial circle, comprised between the meridian of the same place and the meridian of the Fortunate Islands. Because those ancient geographers, wishing to describe the surface of the earth and to investigate the distances of places by measurement original: "stadismo", placed the first degree of longitude in the west, that is, in the Fortunate Fortunate Islands.Islands, which are now called the Canaries: then, according to the succession of numbers, they depicted the circumference of the earth step by step through the south toward the east. This longitude, I say, we have entitled on the flat layout (which they call a Map) as follows, with Hebrew letters (because longitude, if we look at the North, is directed from right to left in the Hebrew manner) "Helicha Haaretz," which sounds "the passage or way of the earth." We will teach with some brevity in the following propositions by what method the longitude of each place is to be discovered. Otherwise, with God's help, we have decided to publish it much more accurately in our Astrolabe, and also in the flat Meteoroscope, from our treasury of mathematical discipline. How the longitude of the orb is to be explored in our flat design, and also in a solid body, I shall now complete. Thus, longitude is distinguished by meridians, which meet around the poles. Whence, the degrees measuring the arc of the equator, between the first degree of longitude (which closes the west) and the meridian that passes through the place of your dwelling, are called degrees of longitude.

Diagram showing two globes on the left and a large elliptical projection on the right, illustrating the measurement of longitude.