CHAPTER I. 



COSMICAL GEOLOGY. 



Cosmogony.- It does not come within the domain of geology 

 to investigate the origin of the universe and of solar and 

 planetary systems. Yet such investigations are so closely 

 associated with the origin and earliest history of the earth, 

 that the results attained by astronomical researches have at 

 all times exerted an influence upon the views of geologists. 

 Visionary speculations about the beginnings of the universe 

 and the earth were much in favour during the eighteenth 

 century, and almost every geological work of a general char- 

 acter had an astronomical introduction. In the early part of 

 the nineteenth century speculation gave place before the great 

 discoveries that were being made in astronomical physics. 

 The explanation given by Kant and Laplace of the origin of 

 the universe and the solar system found general acceptance, 

 and further speculations on cosmogony and geogeny were 

 thought to be either unnecessary for the immediate purposes 

 of geology as a science, or were discouraged on account of 

 their tendency to be wholly theoretical. Thus there followed 

 a long period during which the cosmical aspects of geology 

 made little advance. 



In the year 1871, at Brunswick, Helmholtz gave expres- 

 sion in a popular lecture to the current conception of the 

 earth's origin, based upon the principles of Kant and Laplace: 

 "Our solar system was originally a chaotic nebular ball; at the 

 beginning, when the nebular mass extended as far as the path 

 of the outermost planets, many millions of cubic miles could 

 contain scarcely one gramme of mass. At the time when this 

 nebula became separated from the nebular masses of the 

 neighbouring fixed stars, it possessed a slow movement of 

 rotation. The natural attraction of its parts caused the nebula 

 to condense, and in proportion as it condensed, rotation must 



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