PUNISHING A SENIOR WRANGLER. 155 



who was so far from rising to that clearness of view of the truth of his great 

 discovery, which is expressed by the phrase, ' its negation is inconceivable,' that 

 he actually abandoned it for a time, because (through an error in his estimate 

 of the earth's diameter) it did not seem fully to account for the motion of the 

 moon." 



To the first clause in this sentence, I have simply to give a direct 

 denial ; and to assert that neither Newton's '* observations of the 

 movements of the planets," nor other such observations continued by 

 all astronomers for all time, would yield "the great law of attraction." 

 Contrariwise, I contend that when the reviewer says, by implication, 

 that Newton had no antecedent hypothesis respecting the cause of 

 the planetary motions, he (the reviewer) is not only going beyond his 

 possible knowledge, but he is asserting that which even a rudimentary 

 acquaintance with the process of discovery might have shown him 

 was impossible. Without framing, beforehand, the supposition that 

 there was at work an attractive force varying inversely as the square 

 of the distance, no such comparison of observations as that which led 

 to the establishment of the theory of gravitation could have been 

 made. On the second clause of the sentence, in which the reviewer 

 volunteers for my benefit the information that Newton "actually 

 abandoned " his hypothesis for a while because it did not bring out 

 right results, I have first to tell him that, in an early number of the 

 very periodical containing his article,^ I cited this fact (using these 

 same words) at a time when he was at school, or before he went there.' 

 I have next to assert that this fact is irrelevant ; and that Newton, 

 w^hile probably seeing it to be a necessary implication of geometrical 

 laws that central forces vary inversely as the squares of the distances, 

 did not see it to be a necessary implication of any laws, geometrical 

 or dynamical, that there exists a force by which the celestial bodies 

 affect one another ; and therefore doubtless saw that there was no a 

 lyriori warrant for the doctrine of gravitation. The reviewer, how- 

 ever, aiming to substitute for my " confused notions " his own clear 

 ones, wishes me to identify the proposition — Central forces vary in- 

 versely as the squares of the distances — with the proposition — There 

 is a cosmical force which varies inversely as the squares of the dis- 

 tances. But I decline to identify them ; and I suspect that a consid- 

 erable distinction between them was recognized by Newton. Lastly, 

 apart from all this, I have to point out that, even had Newton thought 

 the existence of an attractive force throughout space was an a priori 

 truth, as well as the law of variation of such a force if it existed, he 

 would still, naturally enough, pause before asserting this law, when he 

 found his deductions from it did not correspond with the facts. To 



^ See Essay on " The Genesis of Science," in the British Quarterly Review for July, 

 1854, p. 127. 



^ I do not say this at random. The reviewer, who has sought rather to make known 

 than to conceal his identity, took his degree in 1868. 



