THE EABTH FOEMED GEOLOGICAL 



CHANGES. 



N our version of the romance of nature, we now descend from 

 the consideration of orb-filled space and the character of the 

 universal elements, to trace the history of our own globe. 

 We shall see that it falls into connexion in an interesting 

 manner with the primary order of things indicated by Laplace's 

 Theory. 



The nature of the materials of the externe or crust of our 

 globe, is known to a greater depth than might be supposed, 

 in consequence of the relation of position of its various masses. 

 Confused as these at first appear, an order of arrangement, 

 connected with time, has been detected in them by the labours 

 of modern geologists. It is found that a certain kind of rock, 

 below which there is never, in ordinary circumstances, any 

 other kind, is of crystalline character. Sometimes elevated in 

 naked mountain masses, sometimes found only at great depths 

 below other rocks of a different kind, Granite (for such is its 

 name) appears as the basis rock of the earth's crust ; the form 

 into which the once fluid matter of our planet was primarily 

 resolved, although, in many instances, subjected, under heat, 

 to new movements at times long subsequent. The crystals of 

 granite are of distinct substances quartz, felspar, mica, and 

 hornblende (each of which is, again, a combination of a certain 

 number of the simple or elementary substances) ; two of these, 

 sometimes three, associated in various proportions, compose 

 the rock, which thus appears in many varieties, passing under 

 different names. 



Where granite does not appear upon the surface, or else 

 some other igneous rock, such as will presently be adverted 

 to, we find that great flooring overlaid with rocks of a different 

 character and history namely, what are called Aqueous or 

 Sedimentary Rocks. These are in the form of strata or beds, 

 and have evidently been for the most part produced as a 



