Chap. 18.] 
ACCOTOT OE THE "WOELD 
51 
is equal to the day, in the Spring and in the Autumn, 
when he is opposed to the centre of the earth \ in the Sth. 
degree of Aries and Libra^. The length of the day and the 
night is then twice changed, when the day increases in length, 
from the winter solstice in the Sth degree of Capricorn, and 
afterwards, when the night increases in length from the 
summer solstice in the 8th degree of Cancer^. The cause of 
this inequality is the obliquity of the zodiac, since there is, 
at every moment of time, an equal portion of the firmament 
above and below the horizon. But the signs which mount 
directly upwards, when they rise, retain the light for a longer 
space, while those that are more oblique pass along more 
quickly. 
CHAP. 18. (20.) — ^WHT THTODER IS ASCBIBED TO JTJPITEE. 
It is not generally known, what has been discovered by 
men who are the most eminent for their learning, in con- 
sequence of their assiduous observations of the heavens, that 
the fires which fall upon the earth, and receive the name of 
thunder-bolts, proceed from the three superior stars ^, but 
principally from the one which is situated in the middle. It 
may perhaps depend on the superabundance of moisture from 
the superior orbit communicating with the heat from the , 
inferior, which are expelled in this manner^ ; and hence it 
is commonly said, the thunder-bolts are darted by Jupiter. 
And as, in burning wood, the burnt part is cast off with a 
crackling noise, so does the star throw ofi" this celestial fire, 
bearing the omens of future events, even the part which is 
* " centrmn terrse ; " the equator, the part equally distant from the 
two poles or extremities. 
^ It may be remarked, that the equinoxes did not actually take place 
at this period m the points mentioned by Pliny, but in the 28th degrees 
of Pisces and Yirgo respectively ; he appears to have conformed to the 
popular opinion, as we may learn from Columella, Hb. ix. cap. 14. The 
degrees mentioned above were those fixed by the G-reek astronomers who 
formed the celestial sphere, and which was about 138 years before the 
Christian sera. See the remarks of Marcus in Ajasson, ii. 246 & 373, 374. 
3 The same remark appHes to this as to the former observation. 
* "siderum.'* 
° The hypothesis of the author is, that the excess of moisture in the 
orbit of Saturn, and the excess of heat in that of Mars, unite in the orbit 
of Jupiter and are discharged in the form of thunder. 
e2 
