28 FKAGMENTS OF SCIENCE. 



upon the moon; a body 240,000 miles, or sixty tii 

 the earth's radius, from the earth's centre, 

 virtually weighed the moon, and found that weight 

 be -g-gVo-th of what it would be at the earth's surfa 

 This is exactly what his theory required. I will 

 dwell here upon the pause of Newton after his first 

 dilations, or speak of his self-denial in withholdii 

 them because they did not quite agree with 

 observations then at his command. Newton's action 

 this matter is the normal action of the scientific mil 

 If it were otherwise if scientific men were not 

 tomed to demand verification if they were satisf 

 with the imperfect while the perfect is attainable, tl 

 science, instead of being, as it is, a fortress of adam; 

 would be a house of clay, ill-fitted to bear the buffeting 

 of the theologic storms to which it is periodic 

 exposed. 



Thus we see that Newton, like Torricelli, first pon- i 

 dered his facts, illuminated them with persistent i 

 thought, and finally divined the character of the force 

 of gravitation. But, having thus travelled inward to 

 the principle, he reversed his steps, carried the principle 

 outwards, and justified it by demonstrating its fitness 

 to external nature. 



And here, in passing, I would notice a point which 

 is well worthy of attention. Kepler had deduced his 

 laws from observation. As far back as those observa- 

 tions extended, the planetary motions had obeyed these 

 laws ; and neither Kepler nor Newton entertained a 

 doubt as to their continuing to obey them. Year after 

 year, as the ages rolled, they believed that those laws 

 would continue to illustrate themselves in the heavens. 

 But this was not sufficient. The scientific mind can 

 find no repose in the mere registration of sequence in 

 nature. The further question intrudes itself with 



