GENERAL PRINCIPLES 



GEOLOGY. 



THE time has not yet arrived, when we may presume that the fundamental principles ol 

 Geology are so well understood by the community in general in our country, that no 

 preliminary statements are necessary in a Report intended for general circulation. In the 

 present instance, however, we may be brief. For, in the first place, a large space was 

 devoted to an elucidation of the science in the early Reports on the Vermont Survey by 

 Prof. ADAMS ; and secondly, we have a right to presume upon a great increase of general 

 acquaintance with the subject since that time. Nevertheless, the science has made no 

 little advance within twelve years, and there are certain points which are intimately 

 connected with Vermont Geology, that are only now in a course of development by 

 geologists, and will, therefore, need special attention. 



STRATIFIED AND UNSTRATIFIED ROCKS. 



It is not mere hypothesis, but legitimate theory, which leads geologists, with almost no 

 exception, to the belief that the interior of the earth is now in a molten state, and that at 

 an early date it was entirely melted. But being placed as the earth is, in a medium (the 

 planetary spaces) from 50 to 75 below zero, a crust must have formed over the molten 

 surface, which has been growing thicker up to the present time. This envelope is called 

 the crust of the earth. Geological facts would lead to the conclusion that it cannot be more 

 than a hundred miles thick ; but some astronomical reasoning, which we regard as less 

 satisfactory, increases the thickness to six hundred miles. 



Now the rocks of this crust are found to be of two kinds, the Stratified and IJnstratified. 

 The former are composed of layers like a pile of boards or books, lying upon one another ; 

 though the layers are sometimes curved more or less. Each stratum is also subdivided into 

 extremely thin layers, like the leaves of a book, generally, but not always parallel to the 

 planes of stratification, called laminae in the mechanical deposits, but folia in the schists. 

 The slates have another set of diAdsional planes coinciding more or less with the beds or 

 strata in direction, called cleavage planes, most obvious in common roofing slate. A third 

 set of parallel planes cross the strata in at least two directions, dividing the rock into 

 rhomboidal forms, and called joints. 



The unstratified rocks have no parallel divisional planes, except that sometimes they are 

 jointed, regularly or irregularly. But lamination is always, and cleavage generally absent. 

 This class of rocks are thought always to have been melted by dry heat, or made plastic 



