234 HERSCHEL AND HIS WORK 



had been watching, and still greater changes since 

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

 of it in his Sy sterna Saturnium. " The various appear- 

 ances of this nebula," Herschel writes, " are so instruct- 

 ive that I shall apply them to the subject of the 

 partial opacity of the nebulous matter. . . . For when 

 I formerly saw three fictitious nebulous stars, it will 

 not be contended that there were three small shining 

 nebulosities, just in the three lines, in which I saw 

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

 ing. As well might we ascribe the light surrounding a 

 star, which is seen through a mist, to a quality of 

 shining belonging to that particular part of the mist, 

 which by chance happened to be situated where 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 can 

 exist in a state of opacity, and may possibly be diffused 

 in many parts of the heavens without our being able to 

 perceive it." 



It would be unjust to Herschel to pass over the 

 condemnation of his views, pronounced by Sir David 

 Brewster in his Life of Sir Isaac Newton. Without 

 mentioning the name of William Herschel, or of La 

 Place, who advocated the same views, Sir David writes 

 as one who felt sure that Newton, for mathematical 

 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 scholar and the author of Phalaris, he enters 



1 Life of Newton, ii. 130. 



