234 HI RSCHEL AND HIS WORK 



had been watching, and still greater changes 

 Hoyghens, a century and a half earlier, gave a picture 

 of it in his Sy sterna Satumium. " The various ap; 

 ances of this nebu la." 1 1 rschel writes, " are so inst ruct- 

 hat I shall apply them to the subject of tli<> 

 partial opacity of the nebulous matt r . . . For when 

 I formerly saw three fictitious nebulous stars it will 

 not be contended that there wen tin., small shining 

 M 1'iilosities, just in (he three linrs, in which I saw 

 tin-in, of which two are now gone, and only one remain- 

 ing. As \\vll illicit we ascribe the light surrouinlin^ a 

 star, which is seen through a mist, to ;i <|imlity of 

 shining belonging to that particular part of the mist, 

 which by chance happened to be situate-l win-re the 

 star is seen. If then the former nebulosity of the two 

 stars which have ceased to be nebulous can only be 

 ascribed to an effect of the transit or penetration 

 through nebulous matter which deflected and scattered 

 it, we have now a direct proof that this matter 

 in a state of opacity, and may possibly be dili 

 in many parts of the heavens without our being able to 

 perceive it." 



It would be unjust to Herschel to pass over tin 

 condemnation of his views, pronounced by Sir David 

 Brewster in his Life of Sir Isaac Newton. Without 

 mentioning the name of William Herschel, or < 

 Place, who advocated the same views, Sir David writes 

 as one who felt sure that Newton, for mathem 

 reasons alone, would have taken a side against this 

 Nebular Hypothesis. 1 In the last of the famous four 

 letters written by Sir Isaac to Dr. Bentley, the great 

 classical iud the author of Phalaris, he eutt i> 



1 Life of Newton, ii. 130. 



