TELESCOPES. 



85 



for those between 1" and 2"; the measurement in every 

 case being several times repeated. 13 



During the last few years, two men, unconnected with any 

 industrial profession the Earl of Rosse, at Parson's Town, 

 (about fifty miles west of Dublin,) and Mr. Lassell, at Star- 

 field, near Liverpool, have, with the most unbounded liberality, 

 inspired with a noble enthusiasm for the cause of science, 

 constructed under their own immediate superintendence 

 two reflectors, which have raised the hopes of astronomers 

 to the highest degree. 84 Lassell's telescope, which has an 

 aperture only two feet in diameter, with a focal length 

 of twenty feet, has already been the means of discovering 

 one satellite of Neptune, and an eighth of Saturn, besides 



33 Struve, Stellarum duplicium et multiplicium Menmra 

 micrometricce, pp. 2, 41. 



34 Mr. Airy has recently given a comparative description 

 of the methods of constructing these two telescopes, including 

 an account of the mixing of the metal, the contrivances 

 adopted for casting and polishing the specula and mounting 

 the instruments ; Abstr. of the Astr. Soc., vol. ix. no. 5, March, 

 1849. The effect of Lord Rosse' s six-feet metallic reflector, 

 is thus referred to. (p. 120.) "The Astronomer Royal, Mr. 

 Airy, alluded to the impression made by the enormous light 

 of the telescope : partly by the modifications produced in 

 the appearances of nebula? already figured, partly by the great 

 number of stars seen even at a distance from the Milky Way, 

 and partly from the prodigious brilliancy of Saturn. The 

 account given by another astronomer of the appearance of 

 Jupiter was, that it resembled a coach-lamp in the telescope ; 

 and this well expresses the blaze of light which is seen in 

 the instrument." Compare also Sir John Herschel, Outl. of 

 Astr., 870. " The sublimity of the spectacle afforded by 

 the magnificent reflecting telescope constructed by Lord 

 Rosse of some of the larger globular clusters of nebulae is 

 declared by all who have witnessed it, to be such as no 

 words can express. This telescope has resolved or rendered 

 resolvable multitudes of nebulae which had resisted all inferior 

 powers." 



