PORTION OP THE COSMOS. NEBULvE. 217 



bility of a process of gradual formation of stars from uncon- 

 solidated matter. No other class of cosmical forms, no 

 other objects of contemplative rather than . of measuring 

 astronomy, are so highly fitted to engage and exercise the 

 power of imagination, not simply as a symbolical image of 

 the infinite in space, but also because the examination of 

 different states or forms of being, and their conjectural con- 

 nection as stages of existence at successive periods of time, 

 hold out a hope of insight into an antecedent process of for- 

 mation ( 36 ). 



The historical development of our present degree of know- 

 ledge respecting nebulae teaches us that in this as 'in almost 

 all other departments of natural knowledge, the same oppo- 

 site opinions which are now supported by numerous adhe- 

 rents were long ago similarly defended, although on much 

 feebler grounds. Since the general employment of telescopes, 

 we see Galileo, Dominique Cassini, and the sagacious John 

 Mitchell, regarding all nebulae as remote groups or clusters 

 of stars ; while, on the other hand, Halley, Derham, Lacaille, 

 Kant, and Lambert, maintained the existence of starless 

 nebulous masses. Kepler, (as well as, previous to the appli- 

 cation of telescopic vision, Tycho de Brahe), was a zealous 

 supporter of the theory of the formation of stars from cos- 

 mical nebulous mutter, by the condensation of celestial 

 vapours into spherical bodies. He believed, " cceli materiam 

 tenuissimam" (the nebulosity which shines in the Milky Way 

 with a mild sidereal light) " in unum globum condensatam 

 stellam efnngere f he based his opinion not on a process of 

 condensation taking place in the well-defined, rounded 

 nebulae, for these were unknown to him, but on the sudden 

 shining forth of new stars on the margin of the Galaxy. 



