CHAP. 21. (23.)—OF THE DIMENSIONS OF THE WORLD.
The stadium is equal to 125 of our Roman paces, or 625 feet[1].
Posidonius[2] supposes that there is a space of not less than
40 stadia around the earth, whence mists[3], winds and clouds[4]
proceed; beyond this he supposes that the air is pure and
liquid, consisting of uninterrupted light; from the clouded
region to the moon there is a space of 2,000,000 of stadia,
and thence to the sun of 500,000,000[5]. It is in consequence
of this space that the sun, notwithstanding his immense
magnitude, does not burn the earth. Many persons have
imagined that the clouds rise to the height of 900 stadia.
These points are not completely made out, and are difficult
to explain; but we have given the best account of them that
has been published, and if we may be allowed, in any degree,
to pursue these investigations, there is one infallible geometrical principle, which we cannot reject. Not that we can
ascertain the exact dimensions (for to profess to do this
would be almost the act of a madman), but that the mind
may have some estimate to direct its conjectures. Now it is
evident that the orbit through which the sun passes consists
of nearly 366 degrees, and that the diameter is always the third
part and a little less than the seventh of the circumference[6].
Then taking the half of this (for the earth is placed in the
centre) it will follow, that nearly one-sixth part of the immense space, which the mind conceives as constituting the
orbit of the sun round the earth, will compose his altitude.
That of the moon will be one-twelfth part, since her course
is so much shorter than that of the sun; she is therefore
carried along midway between the sun and the earth[7]. It
is astonishing to what an extent the weakness of the mind
will proceed, urged on by a little success, as in the abovementioned instance, to give full scope to its impudence!
Thus, having ventured to guess at the space between the sun
and the earth, we do the same with respect to the heavens,
because he is situated midway between them; so that we may
come to know the measure of the whole world in inches.
For if the diameter consist of seven parts, there will be
twenty-two of the same parts in the circumference; as if we
could measure the heavens by a plumb-line!
The Egyptian calculation, which was made out by Petosi-
ris and Necepsos, supposes that each degree of the lunar
orbit (which, as I have said, is the least) consists of little
more than 33 stadia; in the very large orbit of Saturn the
number is double; in that of the sun, which, as we have
said, is in the middle[8], we have the half of the sum of these
numbers. And this is indeed a very modest calculation[9],
since if we add to the orbit of Saturn the distance from him
to the zodiac, we shall have an infinite number of degrees[10].
1. Hence the passus will be equal to 5 Roman feet. If we estimate
the Roman foot at 11c˙6496 English inches, we shall have the miliare of
8 stadia equal to 1618 English yards, or 142 yards less than an English
statute mile. See Adam's Roman Antiquities, p. 503; also the articles
Miliare and Pes in Smith's Dictionary of Greek and Roman Antiquities;
and for the varieties of the stadium, as employed at different periods and
in different countries, see the article Stadium. The stadium which Herodotus employed in measurements of Babylon has been supposed to
consist of 490 English feet, while that of Xenophon and Strabo has been
estimated at 505; see Ed. Rev. xlviii. 190. The Abbé Barthelemi
supposes the stadium to be equal to 604 English feet; Anach. Travels,
vii. 284.
2. There appears to have been two individuals of this name, who have
been confounded with each other; the one referred to by Pliny was an
astronomer of Alexandria, who flourished about 260 years B.C.; the other
was a native of Apamea, a stoic philosopher, who lived about two
centuries later; see Aikin's Biog. in loco; also Hardouin's
Index Auctorum,
Lemaire, i. 209.
3. The terms in the original are respectively nubila and
nubes. The
lexicographers and grammarians do not appear to have accurately
discriminated between these two words.
4. The terms in the original are respectively nubila and
nubes. The
lexicographers and grammarians do not appear to have accurately
discriminated between these two words.
5. The words in the text are "vicies centum millia "and "quinquies
millia."
6. Archimedes estimated that the diameter of a circle is to its circumference as 1 to 3c˙1416; Hutton's Diet. in loco. Ptolemy states it to be
precisely as 1 to 3; Magn. Const. i. 12.
7. The author's reasoning is founded upon the supposition of the length
of the sun's path round the earth being twelve times greater than that
of the moon's; the orbit therefore would be twelve times greater and the
radius in the same proportion.
8. "Non inter Lunam et Saturnum, sed inter Lunam et cœlum
affixarum stellarum, medium esse Solem modo dixerat. Quam parum sui
meminit! "Alexandre in Lem. i. 291.
9. "Qui computandi modus plurimum habet verecundiæ et modestiæ,
quum ibi sistit, nec ulterius progreditur." Hardouin in Lemaire, i. 292.
10. "....ad Saturni circulum addito Signiferi ipsius intervallo,..."