56 KEBULAR THEORY. 



of more defined outline and denser structure; thence to 

 others which assumed a globular or spheroidal figure ; thus 

 graduating through every variety of form up to orbs of light, 

 and suns and systems like our own. The conclusions of 

 these distinguished observers were not founded on the 

 changes perceptible in any individual nebula, since the dura- 

 tion of our whole solar system would be inadequate to elicit 

 any change in the condition of any one of these ; but were 

 drawn from the contrast afforded by the numerous bodies of 

 this kind diffused throughout space, which exhibit every stage 

 of change and progression. The solar system was supposed 

 to have been created by this agency. The sun is inferred to 

 have been alike the centre and parent of the system ; 

 existing primarily in the shape of a diffused nebula, it is 

 supposed in the progress of rotation and condensation to 

 have thrown off the planets Neptune, Herschel, Saturn, 

 Jupiter, the asteroids, Mars, the Earth, Venus, and Mercury, 

 while the satellites are presumed to have been cast forth 

 from their primaries.* 



It will readily be perceived that this supposed gaseous 

 origin of our planet contains within itself all the conditions 

 requisite for its succeeding changes; it being considered 

 that the earth has passed from a gaseous to a fluid, and 

 thence to a solid condition, as the varied processes of 

 rotation, refrigeration, and condensation have simulta- 

 neously proceeded; the spheroidal form which it now 

 presents, enlarged at the equator and flattened at the poles, 

 being precisely that which would be assumed by a fluid body 

 rotating on its axis. When the first thin pellicle cooled, and 

 its surface hardened, the general physical divisions of the 

 globe are supposed to have taken place, and the varied 

 phenomena of animal and vegetable existence to have com- 

 menced. 



To the mind unaccustomed to scientific inquiry, the propo- 

 sition that our globe, owes its origin to a mere cloud of 

 vapour, may appear as strange and startling as many other 



* As Lord Ross has resolved, with his monster telescope, many of the nebulse 

 into clusters of stars, the nebular hypothesis must be regarded only as a con- 

 jecture ; it is possible that with instruments possessing greater penetrating 

 power, the whole of the nebulse might be resolved. 



