That a ray of light is a kindling of sudden fire, borne through the air with great rapidity, and displaying an appearance of length; that rain proceeds from the clouds, being a transformation of them into water, whenever the moisture which is caught up from the earth or from the sea, by the sun, is not able to be otherwise disposed of; for when it is solidified, it is then called hoar frost. And hail is a cloud congealed, and subsequently dispersed by the wind. Snow is moisture from a congealed cloud, as Posidonius tells us in the eighth book of his discourse on Natural Philosophy. Lightning is a kindling of the clouds from their being rubbed together, or else broken asunder by the wind, as Zeno tells us in his treatise on the Universe; and thunder is the noise made by them on the occasion of their being rubbed together or broken asunder; and the thunderbolt is a sudden kindling which falls with great violence on the earth, from the clouds being rubbed together or broken asunder, or, as others say, it is a conversion of fiery air violently brought down to the earth. A typhon is a vast thunderbolt, violent and full of wind, or a smoky breath of a cloud broken asunder. A πρηστὴς is a cloud rent by fire, with wind,[93] … into the hollows of the earth, or when the wind is pent up in the earth, as Posidonius says in his eighth book; and that some of them are shakings, others rendings, others emissions of fire, and others, instances of violent fermentation. LXXXII. They also think that the general arrangement of the world is in this fashion; that the earth is in the middle, occupying the place of the centre; next to which comes the water, of a spherical form; and having the same centre as the earth; so that the earth is in the water; and next to the water comes the air, which has also a spherical form. LXXXIII. And that there are five circles in the heaven; of which the first is the arctic circle, which is always visible; the second is the tropical summer circle; the third is the equinoctial circle; the fourth, the winter tropical circle; and the fifth the antarctic, which is not visible. And they are called parallel, because they do not incline to one another; they are drawn however around the same centre. But the zodiac is oblique, cutting the parallel circles. There are also five zones on the earth; the first is the northern one, placed under the arctic circle, uninhabitable by reason of the cold; the second is temperate; the third is uninhabitable because of the heat, and is called the torrid zone; the fourth is a temperate zone, on the other side of the torrid zone; the fifth is the southern zone, being also uninhabitable by reason of the cold.[94]