Explanatory Remarks. 113 



of the simple minerals found in each rock ; and the remaining col- 

 umns, the various systems above referred to. The simple minerals 

 are put down with little order ; without any attempt at class- 

 ification ; it being thought sufficient to refer them to the rocks in 

 which they are found. 



In describing the various rocks in the State, I shall, as far as pos- 

 sible, follow a uniform order ; giving first the mineralogical charac- 

 ters ; next the topography of the formation ; next the dip, direction, 

 &c. of the strata ; next an account of the organic remains ; next of 

 the mineral contents ; and finally, add some theoretical considerations. 

 In many instances, however, this order cannot be observed ; and in 

 others, some of the above particulars will need no notice. 



I was in doubt for a time whether it would be advisable to add any 

 remarks upon the theory of the rock formations, or the explanation of 

 particular phenomena. But such an addition seemed wanting to com- 

 plete my account of the rocks ; and I came to the conclusion to attempt 

 an explanation of all the most important phenomena, which I describe. 

 There will of course be a diversity of opinion concerning many of 

 the theories, and especially concerning the hypotheses, which I shall 

 advance. I have given those which are most satisfactory to my own 

 mind, after consulting several of the most recent, and most able wri- 

 ters upon geological philosophy. While I could not but express plain- 

 ly, my own decided convictions, I hope I have not done it dogmatic- 

 ally. 



A few words more maybe necessary in explanation of the geological 

 map. I have striven to reduce it to such simplicity, that its plan and 

 arrangement will be -obvious by mere inspection. Some things about 

 it, however, may, need elucidation. To avoid confusion and mistake, 

 I have employed but six colors : which, with the exception perhaps of 

 the blue, are so strongly marked, that they can readily be distinguish- 

 ed by candle light. These colors mark off the rocks of the state into 

 what may be regarded as distinct groups : the members of each group 

 with the exception of the fourth, being so nearly related, that they 

 might even be regarded, in most cases, as belonging to the same for- 

 mation ; or if this term be too limited in its meaning, we might resort 

 to the terrain of the French geologists ; a word to which we have 

 no one in English exactly corresponding. The first group, however, 

 embracing all the unstratified rocks, would include more than one 

 terrain, if that term can embrace only the rocks produced during one 

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