208 THE WORLD MACHINE 



doing, he had done ; he had conceived gravity as a measurable 

 force, and himself made the measure. He had established the 

 rate at which bodies fall, shown that it was independent of 

 the slope or angle of the descent, shown that any projectile, 

 rifle-bullet or cannon-ball even, follows this same law and falls 

 to the ground by virtue of this same force. He had even gone 

 further and divined the last needful element of a complete 

 theory ; he had seen with Kepler that not only does a body 

 at rest remain at rest if acted upon by no extrinsic force, but, 

 further than Kepler, that a body in motion remains in motion 

 unless there is some force to stop it. 



The puzzle of the ancients with regard to the movement 

 of the planets and it was Kepler's puzzle, too was the force 

 that kept them going. Galileo showed that once in motion no 

 further force was needful. Unless something got in their way, 

 they would simply keep on going. It was but a step from the 

 earth to the skies, from the movements of terrestrial bodies 

 to those of the heavens ; but ah ! what a step ! Kepler had all 

 but built a bridge ; Galileo had in his hands the keystone that 

 would complete it. Like Kepler, he had read the work of 

 Gilbert. But he, too, could not see the import of the thought 

 and work of his friend, even as Kepler could not see that of his. 



Galileo was deeply interested in the tides ; the true theory 

 of the tides had been worked out by Poseidonius and others, 

 far back in the Greek days. Galileo prided himself as a scholar ; 

 he had studied Archimedes with larger results than any man 

 before or since. He must have known well the writings of the 

 ancients. Kepler, mixing therewith some of his too exuberant 

 fancy, still had a tolerably correct idea. Galileo went all wrong, 

 and going wrong just missed, as Kepler missed, robbing Newton 

 of his fame. He fumbled the movement of the earth and the 

 movement of the oceans. Could he but have caught the true 

 theory, instantly his combining, measuring, experimental mind 

 would have seen that if the moon can draw the tides, the earth 

 may draw the moon. He would have seen in a flash the con- 

 nection between the fall of bodies, the path of a cannon-ball 

 and the path of the moon. 



He would have caught up his pen and calculated the rate of 

 the moon's descent towards the earth each moment, fifty or eighty 

 years before a raw lad had come up from Lincolnshire to Cam- 

 bridge to study mathematics because he was no use on a farm. 



