BY G. R. SMALLEY, ESQ. 351 



obtain very high magnifying power, a result which is more 

 favorable for the gratification of our curiosity than for purposes 

 of scientific utility. And here, for scientific purposes, is the 

 advantage of a refracting over a reflecting telescope. Perfect 

 distinctness is the first essential, and this can be obtained in a 

 high degree by a lens of moderate dimensions, but is most 

 difficult to arrive at in a polished reflector of large dimensions 

 the very curvature of which is more or less irregular at first, and 

 is always liable to alter by the flexure arising from its own 

 weight. And, moreover, perfect distinctness being supposed, as 

 the magnifying power is increased, the degree of illumination of 

 the magnified object is diminished : hence what is gained by 

 apparent enlargement is lost in detail. Amongst those who have 

 been most successful in the construction of reflecting telescopes, 

 we have the well-known names of Sir William and Sir John 

 Herschel, Lassell, Delarue, Nasmyth, and Lord Rosse the first 

 of these commencing with a telescope of 7 feet focal length only, 

 eventually succeeded in producing one of 40 : and the last, at 

 his own expense, with his own designs, under his own immediate 

 direction, and with much of his own personal labour, completed 

 in 1848 a reflector of no less than 53 feet focal length; 

 one of the most interesting results that have been derived from 

 telescopes of such high magnifying powers is the resolution of 

 Nebulae into clusters of stars of definite magnitude ; but beyond 

 this, however interesting they may be, it is questionable whether 

 any important discoveries will ever be made by their means. 



The most important feature of the present time is the division 

 of labour in the different branches of astronomical science, espe- 

 cially amongst amateurs. 



I have already alluded to the very comprehensive nature of 

 observatory work, and were it not for the labour of private 

 observers prompted by their love of knowledge, much would 

 remain unknown, and still more would be left undone. Thus 

 we find some devoting themselves to a careful examination and 

 measurement of the solar spots ; others to a similar examination 

 of the mountains and depths which appear upon the surface of the 

 moon ; some applying the powers of photography to a minute 

 delineation of those objects, and others passing sleepless nights in 



