202 CHILDHOOD OF SCIENCE. 



time the crudest and vaguest notions had existed on the subject 

 of motion and force. Aristotle had divided all motion into 

 natural and violent, and had taught that it was a kind of disposi- 

 tion residing in arid exercised by the moving body. If it fell 

 towards the earth, that was natural motion, and in accordance 

 with its disposition. All other motion was unnatural and soon 

 exhausted itself. Levity or lightness was supposed to be just as 

 much a property of substances as color or density. Thus smoke 

 ascended because it was endued with absolute levity. Air did 

 not press or gravitate on water because it was in its proper place 

 above it ; but stones and earth sank in water because their proper 

 place was beneath it. Water rose in a pump or siphon because 

 nature abhorred a vacuum ; but very unaccountably it abhorred 

 it only thirty-two feet. It was taught that two pounds of lead 

 would fall twice as far in a minute as one pound would ; and 

 that a body would fall twice as far in two minutes as in one. In 

 short, the whole school philosophy was but another name for 

 error and confusion of ideas ; to dispel which Galileo enunciated 

 his three laws of motion, the laws of fluids, of falling bodies, 

 of pneumatics, in a word the established science of mechanics. 

 But far less for these discoveries than for the wit and argument 

 with w r hich he combatted the errors of scholasticism and the 

 inveterate opposition of the church, is he entitled to the tribute 

 of the greatest champion of science. Aristotle had taught and 

 the sacred scriptures implied that the earth was the fixed center 

 about which the heavens and the celestial bodies revolved. The 

 hierarchy of Koine had staked its infalibility on the geocentric 

 hypothesis, and the dreaded inquisition had arrayed its terrors 

 against the heresy of disbelief. Yet Galileo had the hardihood 

 and the genius, at a time when but little was known of the laws 

 of motion, and nothing of the revelations of the telescope, to 

 declare himself the supporter of the Copernican system, and 

 prepared to prove it against all the world. Its opponents argued 

 that if the vast earth rotated daily on its axis, everything mov- 

 able on its surface would be hurled into space like water from 

 the rim of a revolving wheel. Galileo replied that they had 

 entirely mistaken the nature of gravity, which was nothing more 



