64 Feather stonhaugli^ s Geological Report. 



the student for the discrimination of beds ; to show that the 

 strata, with the exception of the intrusive rocks, have come 

 into their places after an invariable succession ; and that the 

 resemblance between the members of this succession in the 

 United States and the order of the European strata is so strong 

 as to warrant the inference that they have been produced by 

 similar and contemporaneous causes. In the remarks which 

 yet remain to be made, other remarkable proofs will be pro- 

 duced of these truths, derived principally from the organic 

 bodies found in these strata. It cannot escape an observer 

 that the rocks upon the habitable surface of the earth, and fre- 

 quently at an elevation of many thousand feet above the level 

 of the ocean, contain fossil shells and their impressions, of 

 animals that could only have existed in salt water ; in some 

 instances the beds are almost entirely composed of them.* 

 Such rocks, then, must have been covered for long periods of 

 time by the ocean. More extensive observation would show 

 that the greater part of the surface of the earth, if not the 

 whole, has once been in that situation. The student will now 

 fmd himself zealously engaged in an inquiry concerning the 

 causes which have either raised the bottom of the ocean from 

 its ancient level, or depressed it to enable the waters to 

 recede. Happily, the progress which has been made in the 

 investigation of facts will enable him in our day to arrive at a 

 satisfactory conclusion, without having recourse to any hy- 

 pothesis whatever. To explain this briefly and succinctly, it 

 must be premised that we can have no practical knowledge of 

 the structure of the earth beyond the depth of its superficial 

 crust, whilst the semi-diameter of the earth exceeds more than 

 five hundred times the thickness of that crust. But the 

 mean specific gravity of the whole is about double that of the 

 crust, a circumstance which proves that the interior is not 



* The limestone near the top, on the north side of the ridge from the foot of 

 which the Bath waters of Morgan county, Virginia, rise, is full of remains of 

 cncrinites and cardia. 



