NEBULJE. 293 



of sequence, promises to afford us an insight into the laws 

 of genetic development. 



The historical development of our knowledge of nebulous 

 bodies teaches us that here, as in the progress of almost every 

 other branch of physical science, the same opposite opinions, 

 which still have numerous adherents, were maintained long 

 since, although on weaker grounds. Since the general use of 

 the telescope, we find that Galileo, Dominique Cassini, and 

 the sagacious John Michell, regarded all nebulaB as remote 

 clusters of stars ; whilst Halley, Derham, Lacaille, Kant, and 

 Lambert, maintained the existence of starless nebulous masses. 

 Kepler (like Tycho Brahe before the invention of the tele- 

 scope) was a zealous adherent of the theory of star-formation 

 from cosmical vapour from condensed conglobate celestial 

 nebulous matter. He believed " cceli materiam tenuissimam 

 (the vapour which shines with a mild stellar light in the 

 Milky Way,) in unurn globum condensatam, stellam effingere" 

 and grounded his opinion, not on the process of condensation 

 operating in defined roundish nebulous spots, (for these w r ere 

 unknown to him,) but on the sudden appearance of new stars 

 on the margin of the Galaxy. 



If we take into account the number of objects discovered, 

 the accuracy of their telescopic investigation, and the gene- 

 ralization of views, the history of nebulous spots, like that 

 of double stars, may be said to begin with William Herschei, 

 Until his time there were not more than 120 unresolved 

 nebuLfi in both hemispheres, whose positions were deter- 

 mined, including even the results of Messier's meritorious 

 labours; and in 1786 the great astronomer of Slough pub- 

 lished the first catalogue, containing 1000. I have already 

 fully pointed out in an earlier portion of this work that the 

 bodies named nebulous stars (i>e0eXoete?9) by Hipparchus 

 and Gemiuus in the Catasterisms of the pseudo-Eratosthenes 



