GENERAL VIEW. 147 



earth and the atmosphere, either through temporary clefts 

 or more permanent openings. Molten masses, issuing from 

 unknown depths, flow in narrow streams down the de- 

 clivities of mountains, sometimes with an impetuous, and 

 sometimes with a slow and gentle motion, until the fiery 

 subterranean fount is dry, and the lava solidifies under a 

 crust which it has itself formed. We thus see new rocks 

 produced under our eyes; whilst those of earlier forma- 

 tion are altered by the influence of heat, rarely in imme- 

 diate contact, more often in proximity. Even when no 

 disruption takes place, the crystalline particles in super- 

 incumbent rocks are displaced, and re-arranged in a denser 

 texture. The waters present formations of an entirely 

 different nature ; concretions of the remains of plants and 

 animals ; deposits of earthy, calcareous, and aluminous 

 matter ; aggregations of finely pulverized rocks, covered with 

 beds of siliceous-shelled infusoria, and with transported soil 

 containing the bones of animals belonging to an earlier state 

 of our globe. These processes of formation and stratification 

 going on before our eyes, in modes so different, and the 

 disruption, flexure, and elevation of rocks and strata, by 

 mutual pressure and by the agency of volcanic forces, lead 

 the thoughtful observer, by simple analogies, to compare the 

 present with the past, to combine actual pha3nomena, to 

 generalize, and to amplify in thought the extent and in- 

 tensity of the forces now in operation. Thus we arrive at 

 the domain of that geological science, long desired and 

 obscurely anticipated, but which, in the last half century, 

 has been placed on the firm basis of legitimate induction. 



It has been acutely remarked, "that much as we have 

 gazed on the planers through large telescopes, we know less 



