310 COSMOS. 



152 clusters of stars; the Southern or Cape Catalogue, 1.239 

 nebulae and 236 clusters of stars. We have, therefore, 3,538 

 for the number of the nebulae throughout the firmament 

 which were given in these catalogues, as not yet resolved 



contain 2,500 objects, viz. 2,303 nebulae and l^* 7 clusters of 

 stars. (Madler, Astr. p. 448.) These numbers were altered in 

 the subsequent and far more exact exploration made by Sir John 

 Herschel (Observations of Nebula? and Clusters of Stars made 

 at Slough with a twenty-feet reflector, between the years 

 1825 and 1833, in the Philosophical Transactions of the Royal 

 Society of London for the year 1833, pp. 365-481). About 

 1,800 objects were identical with those of the three earlier 

 catalogues : but 300 or 400 were temporarily excluded, and 

 more than 500 newly discovered were determined according 

 to Kight Ascension and Declination. (Struve, Astr. Stellaire, 

 p. 48.) The Northern Catalogue contains 152 clusters of stars, 

 consequently 2,307 152=2,155 nebulae ; but in reference to 

 the Southern Catalogue (Observations at fhs Cape, p. 3, 

 6, 7,) we have to subtract from the 4,015 2,307 

 := 1,708 objects, among which there are 236 clusters of stars 

 (see Op. cit. p. 3, 6, 7, p. 128), 233, viz. 89 + 135 + 9, 

 as belonging to the Northern Catalogue, and observed by Sir 

 "William and Sir John Herschel at Slough, and by Messier in 

 Paris. There remain, therefore, for the Cape observations, 

 1,708233=1,475 nebula and clusters of stars, or 1,239 

 nebula alone. We have, however, to add 135 + 9 = 1 44 to 

 the 2,307 objects of the Northern Slough Catalogue, which 

 increase its numbers to 2,451 objects, in which, after sub- 

 tracting 152 clusters, there remain 2,299 nebulas, a number 

 which is not, however, very strictly limited to the latitude of 

 Slough. When numerical relations are to be given in the 

 topography of the firmament of both hemispheres, the author 

 feels that although such data are from their nature variable, 

 owing to the differences in the epochs and the advances of 

 observation, he is bound to have regard to their accuracy. 

 In a sketch of the Cosmos, it must be endeavoured to delineate 

 the condition of science appertaining to a definite epoch. 



