u6 THE WORLD MACHINE 



Even so, and even more, Poseidonius. Though he makes 

 the sun hardly less distant (50,000,000 of miles) ; though he has 

 a truer idea of the sun's immensity than any other man in 

 antiquity, fixing it at 400,000 miles, or at near half the reality ; 

 though he thus conceives it, apparently, as a body seventy times 

 in diameter, therefore three hundred and fifty thousand times 

 in volume the earth, and sets its orbit at near ten thousand times 

 the earth's circumference ; though he seems the first of physical 

 investigators to perceive that the height of the tides is dependent 

 upon the positions of the sun and the moon ; not even he can 

 find it singular that so vast a thing should move in a rigid 

 curve about the earth. It does not seem absurd to him, nor 

 to his near contemporary, Cleomedes, though Cleomedes per- 

 ceives the truth that our globe is a body so comparatively 

 slight that, seen from the distance of the sun, it would appear 

 but a point. It does not seem absurd even to the mechanical 

 and inventive mind of Archimedes, himself the founder of two 

 great branches of mechanical science. 



The failure of the penetrating intellect of the great Syracusan 

 to grasp the truth of the Aristarchan conceptions is the more 

 amazing from the fact that he was the first, apparently, to 

 devise a mechanical representation of the motions of the 

 heavenly bodies ; he was the first world-mechanic. The 

 planetarium he constructed, the orrery of our day, was the just 

 marvel of the ancients. In the Commonwealth of Cicero, there 

 is a naive and charming page that is well worth transcribing 

 here : 



" I recollect that Caius Gallus, who was a man of profound 

 learning, while he was staying at the house of Marcus Marcellus, 

 asked to see a celestial globe which Marcellus' grandfather had 

 saved after the capture of Syracuse, from that magnificent and 

 opulent city, without bringing to his own house any other 

 memorial out of so great a booty ; which I had often heard 

 mentioned on account of the great fame of Archimedes. Its 

 appearance, however, did not seem to me particularly striking. 

 But as soon as Gallus had begun to explain, in a most satis- 

 factory manner, the principle of the machine, I felt that the 

 Sicilian geometer must have possessed a genius superior to 

 anything we usually conceive to belong to our nature. For 

 Gallus assured us that the solid globe, made by the same 



