a Refracting Telescope with ajluid concave lens. 333 



the use of fluids could be removed, that well directed practice 

 would soon lead to the construction of the most perfect and 

 powerful instruments on this principle at a comparatively small 

 expence. I am, for instance, convinced, judging from what has 

 been paid for large object glasses, that my telescope, telescope 

 stand, and the building for observation, with every other re- 

 quisite convenience, have been constructed for a less sum than 

 would be demanded for the object glass only, if one could be 

 produced of the same diameter of plate and flint glass ; and 

 this surely is a consideration which ought to have some weight, 

 and encourage a perseverance in the principle of construction. 

 The telescope, and the particulars relative to it, being thus 

 described, it only remains for me to state the tests to which I 

 have subjected it, and its performance in those cases. 



The first observations of this kind are commonly on Pola- 

 ris. The small star here is of course brilliant and distinct. 

 It is seen best with a power of 1^0, but is visible with a power 

 of 700. 



The small star in Aldebaran is very distinct with a power of 

 120. 



The small star in ct Lyrae is distinctly visible with the same 

 power. 



The small star called by Mr Herschel Debilissima, between 

 4 £ and 5 Lyrae, — whose existence, he says, could not even 

 be suspected in either the 5 or 7-feet equatorial, and invisible 

 also with the 7 and 10-feet reflectors of 6 and 9 inches aper- 

 ture, but seen double with the 20-feet reflector, — is seen very 

 satisfactorily double with this telescope. 



V Persei, marked as double in South and Herschers cata- 

 logue at the distance of 28'', with another small star at the 

 distance of 3' 57", both 7i p, is seen distinctly sixfold, four of 

 the small stars being within a considerably less distance than 

 the remote one of ri marked in the catalogue. And, rejecting 

 this remote star, the principal, and the other four small stars, 

 form a miniature representation of Jupiter and his satellites, 

 three of them being nearly in a line on one side, and the other 

 on the opposite. There are also other small stars within the 

 same distance, but the most remarkable are those arranged in 

 a line as above stated. 



