409 
centric hypothesis was never heard of before it was propounded 
by Copernicus, and is so rational that everybody ought to 
accept it the moment it is advanced. Pythagoras, “ the first 
philosopher,” taught a heliocentric theory 2,000 years before 
Copernicus, and there was also the Egyptian system and the 
theories of Apollonius and Heraclides. The idea of physical 
astronomy ever again becoming completely revolutionized may 
seem monstrous to those who have not gone deeply into 
astronomical problems ; but it should be remembered, that, 
even when the subtile forces of nature were very imperfectly 
known, and when the heavens were supposed to be regulated 
by geometry and mechanical arrangements of various circular 
movements, even then the two greatest mathematicians who 
ever lived, Euclid and Archimedes, as well as Eudoxus, Hip- 
parchus, and Aristotle, all “ deliberately preferred the geocen- 
tric solution of the astronomical phenomena.” * And since 
even a Cambridge wrangler has put forth a plea in favour 
of the Ptolemaic system, and acknowledges the necessity for 
some law of repulsion to counterbalance that of gravity, I 
may now perhaps venture to conclude this paper with a few 
passages from the first tractatef that I published on this 
subject seven years ago, which will express nearly my present 
views, and at least as much of fresh theory as I have any 
inclination now to indulge in : — 
“ Supposing cold to be the cause of gravitation, acting as it were externally, 
and pressing all bodies, in proportion to their matter, towards a centre, from 
every side. And suppose the sun to be in such a centre of the solar system, 
and the effect of its heat to be repulsive, and contrary to the cold causing 
gravitation. Then, the fatal defect in the theory of universal gravitation 
would be supplied ; for when bodies approached the sun they would thus 
again be repelled ; and the more directly and with the greater velocity they 
approached it in their revolutions, the more violent would be their repulsion, 
as, for instance, in the case of comets.” 
“ It also follows from what has been laid down, strange as it now may 
sound, that the heavenly bodies might revolve in crystalline spheres, either 
perfectly round or elliptical, that is, if not attracted towards the centre, as 
was supposed to be the case by a very ancient system of astronomy ; or that 
they could be carried round their centres in circular vortices of ether, or 
some other element, as was held by the Cartesians ; or they could revolve 
if held by some balancing and opposite powers or forces of nature, that could 
really act as centripetal and centrifugal forces of attraction and repulsion, 
both equally constant, and alternately increasing and decreasing, so as to 
* The Astronomy of the Ancients. By Sir G. C. Lewis, Bart., in loc. 
t Vis Inertice Vida, § 137. note, and §§ 142 — 146. 
