26 INDEX CATALOGUE. 



Herschel, W. : Abstracts of Memoirs — Continued. 



A.D. Vol. P. 



1811 101 272 Diffused nebulosity exists in great abundance. 



275 Observations of more than one hundred and fifty square 



degrees of it. 

 277 Its abundance exceeds all imagination. 



Nebulous matter consists of substances that give out light, 



which may have many other properties. 



278-281 Nebulous diffusions contain both milky nebulosity, and 



such as from its faint appearance may be mistaken 



for resolvable. 



278-279 The range of its visibility is confined to very moderate 



limits. 

 280 The purpose for which such great abundance of nebulosity 



may exist, deserves investigation. 

 282 Either greater depth or greater compression of the nebu- 

 lous matter may occasion greater brightness. 



284 Condensation will best account for greater brightness. 

 The condensation of the nebulous matter ascribed to grav- 

 itation. 



285 When a nebula has more than one preponderating seat of 

 attracting matter, it will probably in time be divided. 

 This conception is supported by the appearance of double 



nebulas. 



286 Their double appearance can be no deception. 

 Their nebulosity is derived from one common stock. 



290 This opinion is supported by the remarkable situation of 

 nebulae. 



292 "Which may be seen in Mr. Bode's Atlas Ccelestis. 



293-296 The real form of the nebulous matter of which nebula? 

 are composed may be inferred from their figure. 



299 The form of the nebulous matter of round nebulae is 

 globular. 

 This form is caused by gravitation. 



302 The central brightness of nebulae points out the seat of at- 

 traction. 

 The effect of attraction on the form of the nebulous mat- 

 ter depends on its original expansion, on the time of the 

 action and on the quantity of the attracting matter. 



305 III different stages of condensation pointed out. 



306 Comets may be highly condensed nebula?. 



307 Progressive condensation takes place. 



308 Concentric brightness as well as globular form indicates 



the general gravitation of the nebulous matter. 

 Progressive condensation may be seen in the formation of 

 nuclei. 



