383 
and how honest persons, if well instructed, can repeat the 
story, I do not understand. I can only once more point to the 
printed Transactions of the Royal Society to prove that it is a 
myth. All that Newton had to do with the theory was to 
give it mathematical countenance, and (as is popularly believed) 
to demonstrate its truth. But even if Newton had proved 
— which I beg leave to deny — that gravitating bodies could 
revolve in circles or ellipses round their centres of attrac- 
tion, he must surely have done so in vain, if the real motions 
of the planets are now held to be neither the one nor the 
other ; and, if the sun moves onwards in space, it is simply 
impossible that they can be so. But Newton, also, like 
Kepler and Copernicus, held the sun to be at rest ; the primary 
h} 7 pothesis of the Third Book of the Principia being, “ That 
the centre of the system of the world is immovable.'” 
9. Again, all the demonstrations in the Princvpia are based 
upon the supposition that the heavenly bodies are moving in 
vacuo , or “ in spaces void of resistance ” ; whereas, at the first 
meeting of the British Association for the Advancement of 
Science, it will be found that Professor Airy, the present 
Astronomer Royal, in his Report on Astronomy (1832) stated 
that “ the existence of a resisting medium has been once more 
established in this century by Encke.” So here, again, modern 
astronomers do not believe what Newton taught in the Prin- 
cipia. I may observe, in passing, that when Newton wrote, 
the notion of a resisting medium, or of what was called a 
plenum throughout the universe, as formerly taught by 
Aristotle, was then in vogue, and was the foundation of Des 
Cartes’ system of vortices ; and there is a curious letter from 
Voltaire to a friend, written when he came to England to visit 
Newton, in which he says, in allusion to this change of theories 
from the plenum to a vacuum, (now again reversed in our day !) 
“1 left the world full in Paris, but found it empty in London. 
In France the earth is believed to be shaped like a melon 
[referring to the lemon-shaped water-melon, no doubt], but 
here it is fiat like an orange.” 
10. So, then, if there be really solar motion in space, and if 
there be aresisting medium, through which all theheavenly bodies 
must move, there is not a single demonstration in the Principia , 
whether sound or fallacious, which is in accordance with our 
i( Current Physical Astronomy ” ; and no conclusion at which 
Newton arrived by “ demonstration 33 in his “ immortal work ” 
is now really accepted by modern astronomers. 
11. But I have said (§ 6) that, nevertheless, Newton is in a 
sense responsible for even what the moderns now believe in 
physical astronomy, though discordant with his professed 
demonstrations. And here I must first beg your attention to 
VOL. IV. 2 D 
