Meteorology   

This is the case, first, with those who say that the comet is one of

the planets. For all the planets appear in the circle of the zodiac,

whereas many comets have been seen outside that circle. Again more

comets than one have often appeared simultaneously. Besides, if

their tail is due to reflection, as Aeschylus and Hippocrates say,

this planet ought sometimes to be visible without a tail since, as

they it does not possess a tail in every place in which it appears.

But, as a matter of fact, no planet has been observed besides the

five. And all of them are often visible above the horizon together

at the same time. Further, comets are often found to appear, as well

when all the planets are visible as when some are not, but are

obscured by the neighbourhood of the sun. Moreover the statement

that a comet only appears in the north, with the sun at the summer

solstice, is not true either. The great comet which appeared at the

time of the earthquake in Achaea and the tidal wave rose due west; and

many have been known to appear in the south. Again in the archonship

of Euclees, son of Molon, at Athens there appeared a comet in the

north in the month Gamelion, the sun being about the winter

solstice. Yet they themselves admit that reflection over so great a

space is an impossibility.

An objection that tells equally against those who hold this theory

and those who say that comets are a coalescence of the planets is,

first, the fact that some of the fixed stars too get a tail. For

this we must not only accept the authority of the Egyptians who assert

it, but we have ourselves observed the fact. For a star in the thigh

of the Dog had a tail, though a faint one. If you fixed your sight

on it its light was dim, but if you just glanced at it, it appeared

brighter. Besides, all the comets that have been seen in our day

have vanished without setting, gradually fading away above the

horizon; and they have not left behind them either one or more

stars. For instance the great comet we mentioned before appeared to

the west in winter in frosty weather when the sky was clear, in the