All RAGLES AND SPECIAL PROVIDENCES 



109 



earth is the point from which distances 

 must be measured to bodies attracted by 

 the earth. 



From experiments executed before his 

 time, Newton knew the amount of the 

 earth's attraction at the earth's surface, 

 or at a distance of 4,000 miles from its 

 centre. His object now was to measure 

 the attraction at a greater distance, and 

 thus to determine the law of its diminu- 

 tion. But how was he to find a body 

 at a sufficient distance? He had no 

 balloon, and, even if. he had, he knew 

 that any height to which he could attain 

 would be too small to enable him to 

 solve his problem. What did he do ? 

 He fixed his thoughts upon the moon, a 

 body 240,000 miles, or sixty times the 

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

 He virtually weighed the moon, and 

 found that weight to be -sihniih of what 

 it would be at the earth's surface. This 

 is exactly what his theory required. I 

 will not dwell here upon the pause of 

 Newton after his first calculations, or 

 speak of his self-denial in withholding 

 them because they did not quite agree 

 with the observations then at his com- 

 mand. Newton's action in this matter is 

 the normal action of the scientific mind. 

 If it were otherwise if scientific men 

 were not accustomed to demand verifica- 

 tion if they were satisfied wjth the im- 

 perfect while the perfect is attainable, 

 their science, instead of being, as it is, a 

 fortress of adamant, would be a house of 

 clay, ill-fitted to bear the buffetings of 

 the theologic storms to which it is 

 periodically exposed. 



Thus we see that Newton, like Torri- 

 celli, first pondered his facts, illuminated 

 them with persistent 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 obser- 

 vation. 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 scien- 

 tific mind can find no repose in the mere 

 registration of sequence in nature. The 

 further question intrudes itself with 

 resistless might, Whence comes the 

 sequence? What is it that binds the 

 consequent to its antecedent in nature ? 

 The truly scientific intellect never can 

 attain rest until it reaches the forces by 

 which the observed succession is pro- 

 duced. It was thus with Torricelli ; it 

 was thus with Newton ; it is thus pre- 

 eminently with the scientific man of 

 to-day. In common with the most 

 ignorant, he shares the belief that spring 

 will succeed winter, that summer will 

 succeed spring, that autumn will succeed 

 summer, and that winter will succeed 

 autumn. But he knows still further 

 and this knowledge is essential to his 

 intellectual repose that this succession, 

 besides being permanent, is, under the 

 circumstances, necessary ; that the gravi- 

 tating force exerted between the sun and 

 a revolving sphere with an axis inclined 

 to the plane of its orbit must produce 

 the observed succession of the seasons. 

 Not until this relation between forces 

 and phenomena has been established is 

 the law of reason rendered concentric 

 with the law of nature ; and not until 

 this is effected does the mind of the 

 scientific philosopher rest in peace. 



The expectation of likeness, then, in 

 the procession of phenomena is not that 

 on which the scientific mind founds its 

 belief in the order of nature. If the 

 force be permanent, the phenomena are 

 necessary, whether they resemble or do 

 not resemble anything that has gone 

 before. Hence, in judging of the order 

 of nature, our inquiries eventually relate 

 to the permanence of force. From 

 Galileo to Newton, from Newton to our 

 own time, eager eyes have been scanning 



