82 IHSSKUTATlOfl SECOND. [pahtii. 



to emerge into the rarer medium, but will force them to 

 return back into the transparent body. Thus the reflec- 

 tion of light at the second surface of a transparent body 

 is produced, not by the repulsion of the medium in which 

 it was about to enter, but by the attraction of that which 

 it was preparing to leave. 



The first account of the experiments from which all 

 these conclusions were deduced, was given in the Philoso- 

 phical Transactions for 1672, and the admiration excited 

 by their brilliancy and their novelty may easily be imagin- 

 ed. Among the men of science, the most enlightened 

 were the most enthusiastic in their praise. Huygens, 

 writing to one of his friends, says of them, and of the 

 truths they were the means of making known, " Quorum 

 respectu omnia hue usque edita jejunia sunt et prorsus 

 puerilia.^ Such were the sentiments of the person who, 

 of all men living, was the best able to judge, and had the 

 best right to be fastidious in what related to optical ex- 

 periments and discoveries. But all were not equally can- 

 did with the Dutch philosopher ; and though the discove- 

 ry now communicated had every thing to recommend it 

 which can arise from what is great, new and singular ; 

 though it was not a theory or a system of opinions, but 

 the generalization of facts made known by experiments ; 

 and though it was brought forward in the most simple 

 and unpretending form, a host of enemies appeared, each 

 eager to obtain the unfortunate pre-eminence, of being the 

 first to attack conclusions, which the unanimous voice of 

 posterity was to confirm. In this contention, the envy 

 and activity of Hook did not fail to give him the advan- 

 tage, and he communicated his objections to Newton's con- 

 clusions concerning the lefrangibility of light in less than a 

 month after they had been read in the Royal Society, 

 lie admitted the accuracy of the experiments themselves. 



