CELESTIAL PHENOMENA. 69 



the difference between the central body and the surrounding 

 nebulous covering can no longer be detected by our telescopic 

 instruments. 



The magnificent zones of the southern heavens, between 50 

 and 80, are especially rich in nebulous stars, and in com- 



Eressed unresolvable nebulre. The larger of the two Magel- 

 mic clouds, which circle round the starless, desert pole of the 

 South, appears, according to the most recent researches,* as 

 " a collection of clusters of stars, composed of globular clusters 

 and nebula of different magnitude, and of large nebulous spots 

 not resolvable, which producing a general brightness in the 

 field of view, form as it were the back-ground of the picture." 

 The appearance of these clouds, of the brightly beaming con- 

 stellation Argo, of the Milky Way between Scorpio, the 

 Centaur and the Southern Cross, the picturesque beauty, if 

 one may so speak, of the whole expanse of the Southern 

 celestial hemisphere, has left upon my mind an ineffaceable 

 impression. The zodiacal light which rises in a pyramidal 

 form, and constantly contributes, by its mild radiance, to the 

 external beauty of the tropical nights, is either a vast nebulous 

 ring, rotating between the Earth and Mars, or, less probably, 

 the exterior stratum of the solar atmosphere. Besides these 

 luminous clouds and nebulae of definite form, exact and corres- 

 ponding observations indicate the existence and the general 

 distribution of an apparently non-luminous infinitely- divided 

 matter, which possesses a force of resistance, and manifests its 

 presence in Encke's, and perhaps also in Biela's comet, by 

 diminishing their eccentricity and shortening their period of 



* The two Magellanic clouds, Nubecula major and Nubecula minor, 

 are very remarkable objects. The larger of the two is an accumulated 

 mass of stars, and consists of clusters of stars of irregular form, cither 

 conical masses or nebulas of different magnitudes and degrees of con- 

 densation. This is interspersed with nebulous spots, not resolvable into 

 stars, but which are probably star dust, appearing only as a general 

 radiance upon the telescopic field of a twenty-feet reflector, and forming 

 a luminous ground on which other objects of striking and indescribable 

 form are scattered. In no other portion of the heavens are so many 

 nebulous and stellar masses thronged together in an equally small space. 

 Nubecula minor is much less beautiful, has more unresolvable nebulous 

 light, whilst the stellar masses are fewer and fainter in intensity. (From 

 a letter of Sir John Herschel, Feldhuysen, Cape of Good Hope, 13th 

 June, 1836.) 



