1 8 THE BORDERLAND OF SCIENCE. 



nebulae, we find that side by side with that gradual but, 

 in the end, complete change which we have already 

 noted in his views respecting our own Milky Way, 

 there was an equally gradual, and in the end, an equally 

 complete change in his ideas respecting the greater 

 number of the celestial cloudlets. Nor will it be diffi- 

 cult to recognise the way in which each change bore 

 upon the other. Nay, it could readily be shown, if this 

 were the place for a close analysis of Herschel's ideas, 

 that the changes in his views (1) as to the nature of 

 double stars; (2) as to the constitution of our star- 

 system ; and (3) as to the nature of the nebulae, were 

 all part and parcel (perhaps unconsciously to himself) 

 of a modification of the principle itself according to 

 which he interpreted his observations. 



It may be well, as I have already quoted what he 

 wrote in 1802, when his ideas respecting the Milky 

 Way underwent their most marked modification, to 

 quote the remarks with which, in 1811, he introduced 

 his modified views respecting the general constitution 

 of the heavens. 6 1 find,' he says, c that by arranging 

 the nebulas in a certain successive regular order, they 

 may be viewed in a new light, and, if I am not mis- 

 taken, an examination of them will lead to consequences 

 which cannot be indifferent to an inquiring mind. If 

 it should be remarked that in this new arrangement I 

 am not entirely consistent with what I have already in 

 former papers said on the nature of some objects that 

 have come under my observation, I must freely confess 

 that by continuing my sweeps of the heavens, my 



