In each planet one of the four elemental qualities predominates (or perhaps two divide the supremacy) and endows the star with a peculiar nature and power. The sun warms and, to some extent, makes dry, for the nearer it comes to our pole the more heat and drought it produces. The moon, on the contrary, causes humidity, since it is close to the earth and gets the effect of vapors from the latter. Evidently the moon influences other bodies in this way, rendering them soft and producing putrefaction. It also warms a little owing to the light it receives from the sun. Saturn, however, chills and, to some extent, dries, for it is very far from the heat of the sun and the damp mists of the earth. Mars emits a parching heat, as its color and proximity to the sun lead one to infer. Jupiter, situated between cold Saturn and burning Mars, is of a sort of lukewarm nature, but tends more to warmth and moisture than to the other two qualities. So does Venus, but conversely, for it warms less than Jupiter but makes moist more, since its large area catches many damp vapors from the neighboring earth. In Mercury, situated near the sun, moon and earth, neither drought nor dampness predominates; but that planet, incited by its own velocity, is a potent cause of sudden changes. In general, the planets are of good or evil influence according as they abound in the two rich and vivifying qualities, heat and moisture, or in the detrimental and destructive ones, cold and drought. Ptolemy then goes on to discuss the powers of fixed stars. These powers he would seem to make depend chiefly on the relation of the fixed star to the planets or on its position in some constellation. Then he treats of the influence of the seasons and of the four cardinal points, to each of which he assigns some one predominating quality. A discussion of the importance of such things as the twelve signs of the zodiac, the twelve “houses,” the _Trigones_ (equilateral triangles each comprising three signs of the zodiac), and the position of the star in reference to the horizon, ends the first book and also the presentation of fundamental considerations.