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On The Heavens   

horizon. There is much change, I mean, in the stars which are

overhead, and the stars seen are different, as one moves northward

or southward. Indeed there are some stars seen in Egypt and in the

neighbourhood of Cyprus which are not seen in the northerly regions;

and stars, which in the north are never beyond the range of

observation, in those regions rise and set. All of which goes to

show not only that the earth is circular in shape, but also that it is

a sphere of no great size: for otherwise the effect of so slight a

change of place would not be quickly apparent. Hence one should not be

too sure of the incredibility of the view of those who conceive that

there is continuity between the parts about the pillars of Hercules

and the parts about India, and that in this way the ocean is one. As

further evidence in favour of this they quote the case of elephants, a

species occurring in each of these extreme regions, suggesting that

the common characteristic of these extremes is explained by their

continuity. Also, those mathematicians who try to calculate the size

of the earth's circumference arrive at the figure 400,000 stades. This

indicates not only that the earth's mass is spherical in shape, but

also that as compared with the stars it is not of great size.

Book III


WE have already discussed the first heaven and its parts, the moving

stars within it, the matter of which these are composed and their

bodily constitution, and we have also shown that they are

ungenerated and indestructible. Now things that we call natural are

either substances or functions and attributes of substances. As

substances I class the simple bodies-fire, earth, and the other

terms of the series-and all things composed of them; for example,

the heaven as a whole and its parts, animals, again, and plants and

their parts. By attributes and functions I mean the movements of these

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