Archimedes Texts

307
times farther from us at one time, than at another; and also seem
eth to be alwayes of an equal bigness, although it ought to shew
forty times bigger when nearest to us, than when farthest off.

SAGR. But in Jupiter, Saturn and Mercury, I believe that
the differences of their apparent magnitudes, should seem punctu
ally to answer to their different distances.

SALV. In the two Superiour ones, I have made precise ob
servations yearly for this twenty two years last past: In Mercury

there can be no observation of moment made, by reason it suf
fers not it self to be seen, save onely in its greatest digrssieons
from the Sun, in which its distances from the earth are insensibly
unequal, and those differences consequently not to be observed;
as also its mutations of figures which must absolutely happen in
it, as in Venus. And if we do see it, it must of necessity appear
in form of a Semicircle, as Venus likewise doth in her greatest
digressions; but its discus is so very small, and its splendor so
very great, by reason of its vicinity to the Sun, that the virtue
of the Telescope doth not suffice to clip its tresses or adventitious
rayes, so as to make them appear shaved round about. It re

mains, that we remove that which seemed a great inconvenience
in the motion of the Earth, namely that all the Planets moving
about the Sun, it alone, not solitary as the rest, but in company
with the Moon, and the whole Elementary Sphear, should move
round about the Sun in a year; and that the said Moon withal
should move every moneth about the earth. Here it is necessary
once again to exclaim and extol the admirable perspicacity of Co
pernicus, and withal to condole his misfortune, in that he is not
now alive in our dayes, when for removing of the seeming ab
surdity of the Earth and Moons motion in consort we see Jupi
ter, as if it were another Earth, not in consort with the Moon,
but accompanied by four Moons to rovolve about the Sun in 12.
years together, with what ever things the Orbs of the four Medi
cæan Stars can contain within them.

The difficulties
removed that arise
from the Earths
moving about the
Sun, not solitarily,
but in consort with
the Moon.

SALV. Why do you call the four jovial Planets, Moons?

SAGR. Such they would seem to be to one that standing in

Jupiter should behold them; for they are of themselves dark, and
receive their light from the Sun, which is manifest from their be
ing eclipsed, when they enter into the cone of Jupiters shadow:
and because onely those their Hemispheres, that look towards the
Sun are illuminated, to us that are without their Orbs, and near
er to the Sun, they seem alwayes lucid, but to one that should be
in Jupiter, they would shew all illuminated, at such time as they
were in the upper parts of their circles; but in the parts inferi
our, that is between Jupiter and the Sun, they would from Ju
piter be observed to be horned; and in a word they would, to