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There are, Epigenes goes on to say, two classes of comets. One kind sheds its light on all sides without changing its position; the other extends a loose kind of fire in one direction, after the fashion of hair, and passes through among the stars; of the latter kind were the two seen in our own days. The former variety, with hair on all sides, that do not move, are usually low down, and arise from the same causes as beams and torches, that is, from a distempered thick atmosphere that carries in it many of the earth’s exhalations, both dry and moist. Air driven out through narrow apertures is capable of setting on fire the atmosphere situated over it, which is full of elements suitable for feeding a fire; and it is able after that to drive it forward from the clear space, lest from any cause it should fall back and relax its force. After that, it can rise again on the next and following days and set fire to the same spot. As presumptive proof of this, we see winds return during several days at their set time. Rain, too, and storms in other forms recur according to appointment. His opinion may be briefly expressed by saying that he supposes comets to be formed pretty much in the same way as fires excited by whirlwind. There is this one difference, that those whirlwinds are pressed down to earth from a higher region, while these others are raised from earth to the upper regions.