NEBULA. 75 



physical universe, there is an especial fascination in the 

 recognition of that which is becoming, or about to be, even 

 greater than in that which is, though the former be indeed 

 no more than a new condition of matter already existing : 

 or of the act of creation itself, the original calling forth of 

 existence out of non-existence, we have no experience, nor 

 can we form a conception of it. 



Besides the comparison of different stages of development 

 in nebulse which appear more or less condensed towards their 

 centres, observers have believed that they could recognize 

 by direct observation at different epochs, actual changes of 

 form in particular nebulse : in the nebula in Andromeda, 

 for example ; in the nebula in the constellation of the Ship ; 

 and in the filamentous portion of the nebula in Orion. 

 Inequality in the instruments employed, differences in the 

 state of the atmosphere, and other optical circumstances, 

 may indeed invalidate part of these results as true historical 

 elements. 



Neither the irregularly-shaped nebulse (to wliich the name 

 more especially belongs), the separate parts of which are of 

 unequal brightness, and which may, possibly, as their circum-. 

 ference contracts, become finally concentrated into stars, 

 nor the planetary nebulae, whose circular or slightly oval disks 

 show throughout a perfectly equable intensity of faint light, 

 must be confounded with nebulous stars. These are not 

 stars accidentally projected upon a distant nebulous ground, 

 but the luminous nebulous matter itself forms one mass 

 with the body which it surrounds. The often considerable 

 magnitude of their apparent diameter, and the remote dis- 

 tance from which their faint light reaches us, show that both 

 the planetary nebulse and thi nebulous stars must be of 



