2 24 SPECIAL RESULTS IN THE UKANOLOGICAL 



rich as compared with the slow advances previously made, 

 was next obtained by the persevering diligence of Messier : 

 deducting those previously discovered by Lacaille and 

 Mechain, his catalogue of 1771 contained 66 nebulae which 

 had never been recorded before. In the poorly provided 

 Observatoire de la Marine (Hotel de Clugny), his efforts 

 succeeded in doubling the known number of nebulae in both 

 hemispheres ( 376 ). 



These feeble beginnings were followed by the brilliant 

 epoch of the discoveries of William Herschel and of his son. 

 As early as 1779 the elder Herschel began a regular review 

 of the nebulae with a 7 -foot reflector; in 1787 his great 

 40 -foot telescope was completed; and in three catalogues 

 ( 3 77) which were published in 1786, 1789, and 1802, he 

 gave the positions of 2500 nebulae and star-clusters. Until 

 1785, and even almost until 1791, this great observer 

 appears to have inclined, with Mitchell, Cassini, and now 

 Lord Rosse, to regard nebulee, to him unresolvable, as ex- 

 ceedingly remote clusters of stars; but between 1799 and 

 1802, longer occupation with the subject, led him, as for- 

 merly Halley and Lacaille, to embrace the nebular hypo- 

 thesis, and even, with Tycho Brahe and Kepler, that of the 

 formation of stars from the gradual condensation of cosmical 

 vapour. The two views are not, however, necessarily con- 

 nected with each other ( 3 7 8 ). The nebulae and clusters ob- 

 served by Sir WiUliam Herschel were subjected by his son, 

 Sir John Herschel, from 1825 to 1833, to a fresh review, in 

 the course of which he added to his father's list 500 new 

 objects, and published in the Philosophical Transactions for 

 1833 (p. 365 to 481) a complete catalogue of 2307 

 nebulae and clusters of stars. This great work contained 



