74 CELESTIAL PHENOMENA. 



density and magnitude, and partly in that of self-luminous 

 vapour, dispersed in shining nebulous spots or patches. 

 If we consider first the nebulous spots, or cosmical vapour 

 in definite forms, its state of aggregation appears constantly 

 varying. The nebulae present themselves to the eye in the 

 form of round or elliptic disks of small apparent magni- 

 tude, either single, or in pairs which are sometimes con- 

 nected by a thread of light : when their diameter is greater 

 their forms vary, some are elongated, others have several 

 branches, some are fan-shaped, some annular, the ring being 

 well defined and the interior dark. They are supposed to 

 be undergoing various and progressive changes of form, as 

 condensation proceeds around one or more nuclei in confor- 

 mity with the laws of gravitation. Between two and three 

 thousand of such unresolvable nebulae (or, at least, in 

 which no stars have hitherto been discovered by the most 

 powerful telescopes), have already been classed, and their 

 positions determined. 



The genetic evolution, or perpetual process of formation, 

 which appears to be going on in this part of space, has lid 

 philosophical observers to the analogy of organic phaenomena. 

 As we see in our forests, at one time, the same kind of tree 

 in all stages of growth, and receive from this co-existence 

 the impression of progressive development ; so, in the great 

 garden of the universe, we seem to see stars in various stages 

 of progressive formation. The process of condensation, 

 which was* part of the doctrine of Anaximenes and of the 

 whole Ionic school, appears to be here going on before our 

 eyes. This subject of conjoint investigation and conjecture 

 has a peculiar charm for the imagination. Throughout the 

 range of animated existence, and of moving forces in the 



