Dr. Herschel's 'iO-feet Telescope. 343 



Forty-feet reflector. I see six satellites at once; and being 

 perfectly assured that the second is invisible, it becomes 

 evident that Saturn has seven satellites. This new satellite 

 is excessively small." 



These two new satellites he observed many times after- 

 wards, and determined their periods, &c. round Saturn. 

 In another place we find the follov.ing passage ; 



Philosophical Trausaclions for 1800, page 76 : — "Oct. 10, 

 1791. I saw the fourth satellite and the ring of Saturn, in 

 the 40-feet speculum, without an eye-glas«. The magnify- 

 ing power on that occasion could not exceed 60 or 70 ; but the 

 greater penetrating power made full amends for the lowness 

 of the former, &c. Among other instances of the superior 

 effects of penetration into space, I should mention the dis- 

 covery of an additional sixth satellite of Saturn, on the 2fath 

 August 1739, and of a seventh on the 11th September, in 

 the same year, which were first pointed out by this instru- 

 ment." 



Philosophical Transactions for 1800, page 77 : — " Nov. 5, 

 1791. Forty-feet. I see the new sixth satellite much bet- 

 ter with this instrument than with the 20-feet. The fifth 

 also is much larger here than in the 20-feet ; in which it 

 was nearly the same size as a small fixed star, but here it h 

 considerably larger than that star. 



*' Here the superior penetrating power of the 40-fcet te- 

 lescope showed itself on the 6th satellite of Saturn, which 

 is a very faint object, &c. &c." 



Philosophical Transactions for 1790, page 2: — '^ It may 

 appear remarkable that these satellites should have remained 

 so long unknown to us, when, for a century and an half past, 

 the planet to which they belong has been the object of almost 

 every astronomer's curiosity, on account of the singular phae- 

 nomena of the ring. But it will be seen presently, from the 

 situation and size of the satellites, that we could hardly expect 

 to discover them till a telescope of the dimcn.'^ions and 

 aperture of my 40-feet reflector should be constructed ; and 

 I need not observe how m>>ch we, members of this society, 

 must feel ourselves obliged to our royal patron, for his en- 

 couragement of the sciences, when wc perceive that the 



Y 4 discovery 



