1 CONTENTS. 



Page 



VII. On Nebulw. By M. Arago, . . . 307 



Definitions, ...... 307 



Nature of Nebula?, ..... 308 



Historical Sketch of the Discovery of Nebulse, . • 310 



Resolvable Nehnloe, 



Their Form, . . . . . .311 



Circular Nebulce, . . . , • 3 1 1 



Number of Stars contained in certain Globular Nebulae, 313 

 Perforated or Annular Nebuloc, . . . 313 



Nebulas are not uniformly disseminated through all the re- 

 gions of the Heavens, . . . .314 



Nebulae considered in their relations to the surrounding 

 spaces, . . . . . . .314 



The spaces poorest in Stars are near the richest Nebulae, 3 1 4 

 Nebulous Matter. 

 The DiiFused Matter occupies very extensive spaces in the 

 Heavens, . . . . . .315 



The great Luminous spots have no regular form, . 315 



Of the Light of True Nebulae, . . .316 



Distribution of the Phosphorescent Matter in True Nebulae, 317 

 Historical details on the Transformation of Nebulae into 

 Stars, . . . . . . .319 



Of the Condensation the Diffused Matter must undergo in 



order to be transformed into Stars, . . . 321 



Comparative intensities of the total Light of a Nebula, and 



the Condensed Light of a Star, . , .321 



Changes Observed in certain Nebulae, . . . 322 



Planetary Nebulae, . . . . . 323 



Diffused Cosmic Matter, not luminous of itself, and imper- 

 fectly diaphanous, . . , . .325 

 Milky Way. 

 Opinions of the Ancients on the Milky Way. . . 326' 

 Opinions of the Moderns, .... 328 



Herschel's labours on the Milky Way, . . . 330 



Will the Milky Way endure for ever in the form in which 

 we now see it 1 . . . . . 334 



VIII. Some Remarks on the Ancient Peruvians. By Sa- 

 muel George Morton, M.D., . . . 335 



IX. Professor Forbes' Account of his Recent Obser- 

 vations on Glaciers. Communicated in Letters 

 to the Editor, 338 



X. Notes on the Effects produced by the Ancient Gla- 

 ciers of Caernarvonshire, and on the Boulders 

 transported by Floating Ice. By Charles Dar- 

 win, Esq., M.A., F.R.S., and F.G.S., . . 352 



