The third cause of the altitude depends on the form of the heavens, not on that of the orbits; the stars appearing to the eye to mount up and to descend through the depth of the air[218]. With this cause is connected that which depends on the latitude of the planets and the obliquity of the zodiac. It is through this belt that the stars which I have spoken of are carried, nor is there any part of the world habitable, except what lies under it[219]; the remainder, which is at the poles, being in a wild desert state. The planet Venus alone exceeds it by 2 degrees, which we may suppose to be the cause why some animals are produced even in these desert regions of the earth. The moon also wanders the whole breadth of the zodiac, but never exceeds it. Next to these the planet Mercury moves through the greatest space; yet out of the 12 degrees (for there are so many degrees of latitude in the zodiac[220]), it does not pass through more than 8, nor does it go equally through these, 2 of them being in the middle of the zodiac, 4 in the upper part, and 2 in the lower part[221]. Next to these the Sun is carried through the middle of the zodiac, winding unequally through the two parts of his tortuous circuit[222]. The star Mars occupies the four middle degrees; Jupiter the middle degree and the two above it; Saturn, like the sun, occupies two[223]. The above is an account of the latitudes as they descend to the south or ascend to the north[224]. Hence it is plain that the generality of persons are mistaken in supposing the third cause of the apparent altitude to depend on the stars rising from the earth and climbing up the heavens. But to refute this opinion it is necessary to consider the subject with very great minuteness, and to embrace all the causes. It is generally admitted, that the stars[225], at the time of their evening setting, are nearest to the earth, both with respect to latitude and altitude[226], that they are at the commencement of both at their morning risings, and that they become stationary at the middle points of their latitudes, what are called the ecliptics[227]. It is, moreover, acknowledged, that their motion is increased when they are in the vicinity of the earth, and diminished when they are removed to a greater altitude[228]; a point which is most clearly proved by the different altitudes of the moon. There is no doubt that it is also increased at the morning risings[229], and that the three superior planets are retarded, as they advance from the first station to the second. And since this is the case, it is evident, that the latitudes are increased from the time of their morning risings, since the motions afterwards appear to receive less addition; but they gain their altitude in the first station, since the rate of their motion then begins to diminish[230], and the stars to recede.