an astronomer like Ptolemy should represent vapors from the earth as affecting the planets at all. But his discussion is at least an effort, albeit a feeble one, to express the potencies of the planets in physical terms. [Sidenote: Remaining contents of Book One.] Ptolemy goes on to discuss the powers of the fixed stars which seem to depend upon their positions in constellations and their relations to the planets. Then he treats of the influence of the four seasons of the year and four cardinal points, each of which he relates to one of the four qualities, hot, cold, dry, and moist. With a discussion of the signs of the zodiac and their division into Houses and relation in _Trigones_ or _Triplicitates_ or groups of three connected with the four qualities, of the exaltation of the planets in the signs and of other divisions of the signs and relations of the planets to them, the first book ends. [Sidenote: Book Two: Regions.] The second book begins by distinguishing prediction of events for whole regions or countries, such as wars, pestilences, famines, earthquakes, winds, drought, and weather, from the prediction of events in the lives of individuals. Ptolemy holds that events which affect large areas or whole peoples and cities are produced by greater and more valid causes than are the acts of individual men, and also that in order to predict aright concerning the individual it is necessary to know his region and nationality. He characterizes the inhabitants of the three great climatic zones,[515] quarters the inhabited world into Europe, Libya, and two parts for Asia in the style of the T maps, and subdivides these into different countries whose peoples are described, including such races as the Amazons. The effects of the stars vary according to time as well as place, so that the period in which any individual lives is as important to take into account as his nationality. Ptolemy also discusses how the heavenly bodies influence the _genus_ of events, a matter which depends largely upon the signs of the zodiac, and also how they determine their quality, good or bad, and species, which depends on the dominant stars and their conjunctions. Consequently he gives a list of the things which belong under the rule of each planet. The remainder of the second book is concerned chiefly with prediction of wind and weather through the year and with other meteorological phenomena such as comets. [Sidenote: Nativities.]