126 fN STARRY REALMS. 



Fig. 11. The Great Nebula in Orion. 



has a similar effect to the moonbeams, in so far as it 

 greatly detracts from the telescopic effectiveness of the 

 nebulae. In fact, these objects are most of them so faint 

 that the caution I have already given as to the liability to 

 disappointment must be especially remembered. Many 

 of them can only be made out by careful watching, and 

 for the fainter ones an eye specially trained to such work is 

 required. It is for nebulae that the leviathan reflectors have 

 been chiefly constructed. The great mirrors are specially 



