PROBABLE ORIGIN OF NEBUL.E. 309 



nebular hypothesis, I cannot understand how we can 

 consistently deny the existence of gaseous nebulae; for, 

 according to the nebular hypothesis, the central nucleus 

 which constitutes a sun or star, and which exhibits a 

 continuous spectrum, was formed by condensation as 

 surely as the planets or the satellites have been. Were 

 we to go back sufficiently far in the past, we should 

 come to a time when not only our globe but the sun 

 himself consisted of gaseous matter only. If we admit 

 this, then why not also admit that there may be nebulas 

 at the present time in a condition similar to what our 

 sun must formerly have been. 



The gaseous condition of the nebulas seems to follow 

 as a consequence from Mr. Lockyer's theory. For, in 

 order that the materials in the formation of a sun 

 or star may arrange themselves according to their 

 densities, dissociation is requisite ; but there can be no 

 dissociation except in the gaseous condition. 



Star - Clusters. — The wide - spread and irregular 

 manner in which the materials would in many cases be 

 distributed through space after collision, would prevent 

 a nebula from condensing; into a single mass. Sub- 

 ordinate centres of attraction, as was long ago shown 

 by Sir William Herschel (in his famous memoir on the 

 formation of stars*), would be established, around 

 which the gaseous particles would arrange themselves 

 and gradually condense into separate stars, which 

 would finally assume the condition of a cluster. 



Binary, Triple, and Multiple systems of stars will of 

 course be accounted for in a similar manner. 



It is conceivable that it may sometimes happen that 



by the time the materials are broken up and dissipated 



into space, there may not be sufficient heat left to 



convert the fragments into vapour. In this case we 



* "Phil. Trans." for 1811. 



