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PART II. 



^humi^ and General Discicssion. 



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The great length of the preceding division of this contribution to our 

 kuowlodge of the older geological formations of the United States and 

 the adjacent northern region nialvos it necessary for us to offer, in this 

 second and concluding portion of our worlc, but a brief synopsis of the 

 conclusions at which we have arrived in the study of these older I'ocks. 

 We have already set forth, in considerable detail, the theories which 

 American geologists have held at various times in regard to those older 

 .crystalline rocks to which the names Archaean and Azoic have been com- 

 monly applied, and in doing this we have had special reference to the 

 necessity or possibility of dividing that scries of rocks into two or more 

 distinct groups. We have given the evidence on which these various 

 theories were based with considerable detail, because the facts which 

 developed themselves, as we pursued our inquiry, were so extraordinary 

 that we felt it to be doubtful whether our statements would bo accepted 

 as trutliful unless we presented the reader with the means of verifying 

 them at once, on the spot, without the necessity of examining a long 

 series of volumes, some of which are only to be obtained with the 

 greatest difficulty. More work has, however, been done by us, both in 

 the field and in the laboratory, in the investigation of the subject here 

 discussed, than the cursory reader of the present article' would per- 

 haps bo inclined to suppose; and we trust that the opportunity may 

 yet be furnished us for carrying this work still farther in the same 

 direction, and for presenting the whole body of the results which we 

 have reached, as well as those which may hci'caftcr be attained, in a 

 fuller form than it is possible for us to do at the present time. 



We think that it is impossible for any unprejudiced worker in this 

 department of science to peruse with care the preceding pages, and not 

 feel obliged to admit that the geology of a lai-ge portion of this country, 

 and especially tliat of Canada and New England, is in an almost hope- 

 less state of confusion. AVe think that it must have been made clear 

 to the candid mind, that tlie geologist would fmd himself com])letcly 

 balllod who should endeavor to obtain any definite knowledge of the real 



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