n8 THE WORLD MACHINE 



ranged in the scheme of Apollonius of Perga, he whose ideas 

 seem most deeply to have influenced Coppernicus. 



From this, to set the earth among the planets was but a 

 step. No, not a step, it was a leap across a chasm, the abyss 

 that lay between the old geometric world-conceptions and the 

 new. The mind of Aristarchus could make the leap ; Archi- 

 medes, Apollonius, Eratosthenes, Hipparchus, Poseidonius, 

 Cleomedes, Ptolemy, and the rest could not. On the other 

 side one giant figure stands alone. 



In the planetarium, as constructed by Archimedes, the five 

 planets which, in the lack of the telescope, could be known, 

 seem to have been placed in their proper order, save in this 

 one regard : their orbits centred in the earth. How a man 

 with a brain to work out and the cunning hand to build such 

 a mechanism could thus stop short, passes understanding. He 

 was at once one of the greatest mathematicians and inventive 

 geniuses that ever lived. He had in his hands, and was, so 

 far as we know, the first actually to employ that happy com- 

 bination of the three sciences which have made possible the 

 marvellous attainments of modern astronomy. Yet more, his 

 studies and discoveries in mechanics were leading him straight 

 toward that mechanical explanation of planetary motion which 

 immortalised the name of Isaac Newton. He was familiar 

 with the problems of the ellipse eighteen centuries before 

 Kepler's birth ; the idea of a centre of gravity was his idea ; 

 he was even a measurer of the force of gravity. One further 

 step and the discoveries of Galileo, and perchance of Kepler 

 and of Newton too, might have been perfected before the 

 Roman dominion had set heel upon Hellenic culture, and before 

 the gospel of an avenging Jehovah had been carried beyond 

 the confines of the little country of Palestine to make of truth 

 blasphemy. 



It was all so astonishing, they came so near : it may lend 

 some helpful insight into the workings of the human mind to 

 consider attentively their failure. 



