PORTION OF THE COSMOS. NEBULAE. 229 



mical bodies of all dimensions and of all degrees of density. 

 We touch here almost involuntarily on the ancient dispute 

 in philosophy on primitive fluidity and composition from 

 distinct molecular particles, which is indeed more accessible 

 to mathematical treatment. Let us hasten to return to that 

 which is purely objective in the phenomenon. 



Among 3926 (2451 + 1475) recorded positions, [be- 

 longing : a, to the portion of the firmament visible at 

 Slough, and which for the sake of brevity we will here call 

 the northern heavens, (according to three catalogues of 

 Sir William Herschel, from 1786 to 1802, and the above- 

 mentioned review published by his son in the Phil. Trans, 

 for 1833) ; b } to the part of the southern heavens visible 

 from the Cape of Good Hope, according to the African 

 Catalogue of Sir John Herschel,] there are contained both 

 nebulas and clusters of stars. However intimately these 

 objects may in truth be related to each other, yet in order 

 to mark the state of our knowledge at a definite epoch I 

 have reckoned each class separately. I find ( 392 ) in the 

 northern catalogue, 2299 nebulae and 152 clusters of stars; 

 in the southern or Cape catalogue, 1239 nebulae and 236 

 star-clusters. This makes for the whole firmament the 

 number of nebulas registered in these catalogues as not 

 having yet been resolved into stars, 3538. This number 

 would be raised to 4000 by taking into the account three 

 or four hundred objects seen by the elder Herschel ( 393 ) 

 and not redetermined by his son, as well as 629 observed 

 at Paramatta by Dunlop with a 9-inch Newtonian reflector, 

 and of which only 206 were transferred by Sir John Her- 

 schel to his catalogue ( 394 ), A similar result has also been 

 very recently published by Bond and by Madler. Accord- 



