VAEIETY OP ASPECT, ETC. 17 



for the most part on the western coasts. This 

 imparts a corresponding Variety to the eastern 

 and western shores. The latter are generally 

 bold and precipitous, the former comparatively 

 tame and low. The natural productions of the 

 soil, too, exhibit a corresponding difference. In 

 the latter they are scanty compared with the 

 luxuriance they exhibit in the former. 



To those acquainted in any considerable degree 

 with the variety of aspect presented by our sea- 

 shores, a view of the geological phenomena on 

 which that variety so much depends can hardly 

 fail to prove interesting. We shall, therefore, 

 exhibit to the reader such a sketch as is com- 

 patible with the nature of this work, in the form 

 of a Geological Tour along the Coast. It will, 

 however, facilitate our design to take a rapid 

 survey of the chief divisions of geological science. 



The solid materials of the globe are by geo- 

 logists understood to consist of the igneous rocks 

 or those left in their present condition by the 

 action of heat and the aqueous formations, or the 

 strata originating in the action of water. These 

 two great classes comprehend, it need hardly be 

 added, a great number and variety of rocks and 

 strata, more or less distinguished from each other 

 by peculiarities of structure and composition. 

 The " igneous rocks " are of great value in all 

 geological investigations. They are the monu- 

 ments of vast organic convulsions, caused by 

 stupendous force to which the surface of our 

 planet has been subjected, and they have acted a 

 c 



