THE NEBULAR HYPOTHESIS. 653 



subsequently developed during the processes which brought about its 

 organization ? According to the preceding view of the structure and 

 constitution of a nebulous mass, the idea of the chaotic matter beinsc 

 maintained in a diffused and attenuated condition through the agency 

 of heat, is by no means necessary. Indeed, the assumption that the 

 primitive matter of the universe existed in a diffused gaseous condition, 

 through the agency of excessive heat, is itself, prima facie, improbable. 

 If it were absolutely universal, what became of the heat, and how did 

 the cooling and condensation commence ? Even if we suppose that 

 the chaotic matter existed in enormous detached masses, what an in- 

 conceivable amount of heat must have been created, merely to be dis- 

 sipated throughout the infinitudes of space ! Such a view ill accords 

 with our conceptions of the economy of the Creator's operations.. 



According to the views previously announced, the original concen- 

 tration of the nebulous matter about a central nucleus was not the 

 result of cooling and contraction, but of a gradual process of aggre- 

 gation of discrete bodies under the action of mutually-attractive forces. 

 Now, in the collisions and frictions necessarily incident to this process 

 of aggregation, we have an indefinite supply of heat. The establish- 

 ment of the " Dynamical Theory of Heat," on the sure basis of experi- 

 ment and observation, assures us that when motion is checked or 

 arrested, it is transformed into heat. Hence, we see that the collisions 

 and destruction of velocity, incident to the process of aggregation, 

 while imparting a motion of rotation to the nebulous mass, at the same 

 time evolved heat, more or less, throughout its structure and espe- 

 cially toward the nucleus, where the bodies, whose velocities had 

 been checked, were gradually subsiding. The larger portion of the 

 "dynamical energy" of the crowd of bodies aggregating toward the 

 nucleus, was thus transformed into heat a smaller portion remaining 

 in the motion of rotation of the solar nebula. This view makes the 

 heat- and light-producing process continuous and gradual, and the true 

 gaseous and fused conditions of the nebula, subsequent states, induced 

 by the evolution of intense heat. 



We thus reach a lofty point of view. Given diffused or chaotic 

 matter, and mutual attraction, and the whole machinery of the Nebu- 

 lar Hypothesis is set in action! The " star-dust," or "world-stuff" 

 begins to aggregate heat is evolved rotation is imparted and all 

 the apparatus required for the formation of suns, planets, and satel- 

 lites, is established ! Assuming that the processes of aggregation and 

 heat-evolution had so far progressed that the rotating spheroid con- 

 sisted of a more or less continuous mass of liquid or gas, extending far 

 beyond the orbit of Neptune, and we are furnished with all the con- 

 ditions assumed by Laplace. 



It is unnecessary to follow the lecturer in his exposition of Laplace's 

 reasoning, by which it was shown, upon mechanical principles, that, 

 as the rotating spheroid slowly contracted and condensed by the grav- 



