26 COSMOS. 



from 1786 to 1802, and the above-named great exploration 

 of the heavens published by his son in the Philos. Tiansact 

 of 1833 ; and h. to the portion of the soutliern heavens visi' 

 ble at the Cape of Good Hope, according to Sir John Her- 

 schel's African Catalogues, nebulse and clusters of stars are 

 set down indiscriminately together. I have, however, deeme^l 

 it best, notwithstanding the natural affinity of these objects, 

 to enumerate them separately, in order to indicate a definite 

 epoch in the history of their discovery. I find that the North- 

 ern Catalogue^ contains 2299 nebulse and 152 clusters of 

 stars ; the Southern or Cape Catalogue, 1239 nebulse and 

 236 clusters of stars. We have, therefore, 3538 for the num- 

 ber of the nebulse throughout the firmament which were given 

 in these catalogues as not yet resolved into clusters. This 

 number may, perhaps, be increased to 4000, if we take into 

 account 300 or 400 seen by Sir William Herschel,t but not 

 again determined, and the 629 observed by Dunlop at Para- 



* The data on which these numbers are based require some expla- 

 nation. The three catalogues of the elder Herschel contain 2500 objects, 

 viz., 2303 nebulte and 197 clusters of stars. (Madler, ^s^r., p. 448.) 

 These numbers were altered in the subsequent and far moi'e exact ex- 

 ploration made by Sir John Herschel (Observations of Nebulae and Clus^ 

 ters of Stars made at Slough with a twenty-feet I'etlector, between the 

 years 1825 and 1833, in the Philosophical Transactions of the Royal 

 Society of London for the year 1833, p. 365-481). About 1800 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 Right Ascension and Declination. (Struve, 

 Astr. Stellaire, p. 48.) The Northern Catalogue contains 152 clusters 

 of stars, consequently 2307 — 152=^2155 nebuhe ; but, in reference to 

 the Southern Catalogue {Observations at the Cape, p. 3, § 6, 7), we have 

 to subtract from the 4015 — 2307=1708 objects, among which there are 

 236 clusters of stars (see Op. cit., p. 3, § 6, 7, p. 128), 233, viz., SO-j- 

 135-^9, as belonging to the Northern Catalogue, and observed by Sir 

 William and Sir Juhn Herschel at Slough, and by Messier in Paris. 

 There remain, therefore, for the Cape observations, 1708 — 233=1475 

 nebulae and clusters of stars, or 1239 nebulise alone. We have, how- 

 ever, to add 135-|-9=^144 to the 2307 objects of the Northern Slougii 

 Catalogue, which increase its numbers to 2451 objects, in which, after 

 subtracting 152 clusters, thei'e remain 2299 nebula;, a numl)er which 

 is not, however, very strictly limited to the latitude of Slough. Wheit 

 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 tlie diflferences 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 endeavored to delineate the coi> 

 dition of science appertaining to a definite epoch. 



t Sir John Her.schel says, in his Observations at the Cape, p. 134, 

 * There are between 300 and 400 nebulae of Sir William Herschel's Cat 

 ai'jgue still unobserved by me : for the most port, very faint objects '' 



