408 TWO CLASSES OF KEBULJE. SECT. XXXVI. 



his father's observations, and added 800 nebulas to the catalogue 

 before he went to the Cape of Good Hope, in order to complete 

 the survey of the heavens. On his return he published a cata- 

 logue of 2049 nebulas of the southern hemisphere, of which 500 

 were previously unknown, with their position in the heavens. 

 In a work unparalleled for elegance of style, depth of knowledge, 

 and originality of views, he has given engravings from his draw- 

 ings of the most remarkable objects, so that whatever changes 

 may take place, in their form, place, or condensation, will be 

 known by astronomers of future ages. 



Though infinite in variety, the nebulas are of two distinct 

 classes ; one consists of patches of great dimensions, capriciously 

 irregular, assuming all the fantastic forms of clouds, now bright, 

 now obscure ; sometimes like vapour flying before the wind ; 

 sometimes stretching long arms into space. Many present an 

 ill-defined surface, in which it is difficult to say where the centre 

 of the greatest brightness is. Large portions are resolvable into 

 stars ; many have a granulated appearance, as if they were re- 

 solvable ; and others probably are not so merely from the small- 

 ness and closeness of the stars, and possibly from their remote- 

 ness, indicating the complex and irregular form the Milky Way 

 would present if seen from a distance. A wonderful nebula of 

 this kind is visible to the naked eye in the constellation of Orion ; 

 it is of vast extent, sending branches even into the southern 

 hemisphere ; and, although Lord Rosse's telescope has resolved 

 much that had hitherto resisted others, there are parts that still 

 maintain their nebulous appearance from extreme remoteness, 

 presenting a kind of mottled aspect, like flocks or wisps of wool, 

 or mackerel sky. There can be no doubt of its being an un- 

 fathomable congeries of stars, which there is reason to believe has 

 changed its form in some parts within the last fifty years. Vast 

 multitudes of nebulas of this kind are so faint as to be with diffi- 

 culty discerned at all till they have been for some time in the 

 field of the telescope, or are just about to quit it. Occasionally 

 they are so vague, that the eye is conscious of something being 

 present, without being able to define what it is ; but the un- 

 changeableness of its position convinces the mind that it is a real 

 object "an image was before mine eyes, but I could not discern 

 the form thereof." 



No drawing can give an idea of the boundaries of such nebulas 



