for the year 1870. xxiii 



true state of the case, and, on the other, to strengthen it by- 

 magnifying its defects, or asserting the existence of 

 imaginary ones, have left the public mind in a state of doubt 

 on the point. When it was decided by the committee of the 

 Royal Society of London that the Melbourne telescope was 

 to be a four-feet reflector, it was hoped, as is our wont, we 

 should get one better than any other ; but although our 

 hopes are not fully realised in that respect, we know we 

 have the result of the best efforts of one of the most 

 renowned opticians, and may feel satisfied that if it does not 

 excel, it quite equals, every other of its size that has yet been 

 made. There are only about three telescopes in the world of 

 like dimensions, all reflectors ; there is none similar in form 

 to oars except in much smaller size, so the experience both 

 in the construction and use of such giant instruments is 

 extremely Hmited. 



Large telescopes always disappoint dilettante observers, and 

 often at first even experienced astronomers. It is only when 

 in the hands of the patient, plodding, discriminating worker, 

 that they reveal the mysteries of deep space, and that often 

 fitfully, perhaps for a few seconds only in the course of hours. 

 Each short moment, however, when the cylinder of 

 atmosphere through which the star (or nebula) light passes 

 to the mirror is favourable for its transmission, becomes to 

 such astronomers the opportunity for result and discovery. 



The Great Melbourne Telescope, like Mr. Lassell's Lord 

 Rosse's, Sir John Herschel's reflectors, the Dorpat and 

 Harvard refi-actors, is not a perfect telescope. No perfect 

 telescope, large or small, has ever yet been constructed. The 

 small appear comparatively more perfect from the less light 

 they collect, and the less power that can be used with them, 

 and consequently the less eflect of atmospheric influence ; but 

 if a similar perfection of figure a,s belongs to the best 

 achromatic or reflector ever constructed on a small scale be 



