Archimedes Texts

SAGR. I am what ever pleaseth Salviatus, but I pray you,
let us not sally out into another kind of digression complemental;
for at this time I am a Philosopher, and in the Schools, not in the
Court.

SALV. Let our contemplation begin therefore with this consi
deration, that whatsoever motion may be ascribed to the Earth,
it is necessary that it be to us, (as inhabitants upon it, and conse
quently partakers of the same) altogether imperceptible, and as if
it were not at all, so long as we have regard onely to terrestrial
things; but yet it is on the contrary, as necessary that the same

motion do seem common to all other bodies, and visible ob
jects, that being separated from the Earth, participate not of the
same. So that the true method to find whether any kind of motion
may be ascribed to the Earth, and that found, to know what it
is, is to consider and observe if in bodies separated from the
Earth, one may discover any appearance of motion, which e

qually suiteth to all the rest; for a motion that is onely seen, v. gr.
in the Moon, and that hath nothing to do with Venus or Jupiter,
or any other Stars, cannot any way belong to the Earth, or to
any other save the Moon alone. Now there is a most general and
grand motion above all others, and it is that by which the Sun,

the Moon, the other Planets, and the Fixed Stars, and in a word,
the whole Universe, the Earth onely excepted, appeareth in our
thinking to move from the East towards the West, in the space of
twenty four hours; and this, as to this first appearance, hath no
obstacle to hinder it, that it may not belong to the Earth alone,
as well as to all the World besides, the Earth excepted; for the
same aspects will appear in the one position, as in the other.
Hence it is that Aristotle and Ptolomy, as having hit upon this con

sideration, in going about to prove the Earth to be immoveable,
argue not against any other than this Diurnal Motion; save onely
that Aristotle hinteth something in obscure terms against another
Motion ascribed to it by an Ancient, of which we shall speak in
its place.

The Earth can
have no other mo
tions, than those
which to us appear
commune to all the
rest of the Vni
verse, the Earth
excepted.

The Diurnal Mo
tion, seemeth com
mune to all the V
niverse, save onely
the Earth excepted.

Aristotle and
Ptolomy argue a
gainst the Diur
nal Motion attri
buted to the Earth.

SAGR. I very well perceive the necessity of your illation: but
I meet with a doubt which I know not how to free my self from,
and this it is, That Copernicus assigning to the Earth another mo
tion beside the Diurnal, which, according to the rule even now laid
down, ought to be to us, as to appearance, imperceptible in the
Earth, but visible in all the rest of the World; me thinks I may
necessarily infer, either that he hath manifestly erred in assigning
the Earth a motion, to which there appears not a general corre
spondence in Heaven; or else that if there be such a congruity
therein, Ptolomy on the other hand hath been deficient in not con
futing this, as he hath done the other.