‹‹‹ Vitr. 1.6.8 | Table of Contents | Vitr. 1.6.10 ›››
9Those who are accustomed to the names of so many winds, will perhaps be surprised at our division of them into eight only; but if they reflect that the circuit of the earth was ascertained by Eratosthenes of Cyrene, from mathematical calculations, founded on the sun’s course, the shadow of an equinoctial gnomon, and the obliquity of the heavens, and was discovered to be equal to two hundred and fifty-two thousand stadia or thirty one millions and five hundred thousand paces, an eighth part whereof, as occupied by each wind, being three millions nine hundred and thirty-seven thousand five hundred paces, their surprise will cease, because of the number of impediments and reverberations it must naturally be subject to in travelling such distance through such varied space.
9Those who know names for very many winds will perhaps be surprised at our setting forth that there are only eight. Remembering, however, that Eratosthenes of Cyrene, employing mathematical theories and geometrical methods, discovered from the course of the sun, the shadows cast by an equinoctial gnomon, and the inclination of the heaven that the circumference of the earth is two hundred and fifty-two thousand stadia, that is, thirty-one one million five hundred thousand paces, and observing that an eighth part of this, occupied by a wind, is three million nine hundred and thirty-seven thousand five hundred paces, they should not be surprised to find that a single wind, ranging over so wide a field, is subject to shifts this way and that, leading to a variety of breezes.