INTRODUCTION. 83 



The facts which I have here brought together and presented, as I 

 believe, in a new combination, and the principles enunciated as the 

 results of my investigations upon the phenomena exhibited over a large 

 area of country, may, I hope, aid in elucidating certain questions in 

 geology, which have hitherto been surrounded with difficulties. After 

 the brilliant discussions of the problem of the Appalachian chain by 

 the brothers Rogers, and other able geologists, and the masterly eluci- 

 dation of their beautiful structure, there is certainly little left to be 

 done in this regard ; and I cannot hope to offer anything so full of 

 interest. At the same time, it does not appear to me that in any of our 

 discussions, sufficient importance has been given to the influence of 

 this large accumulation of matter along the Appalachian zone ; nor to 

 the necessary and consequent effect of this accumulation. The depo- 

 sition along current lines (or shore lines), and the spreading out and 

 thinning of the same deposits on receding from this line, is all in 

 accordance with the elementary teachings of geology. We know, more- 

 over, from the nature of the principal limestone formations, and the 

 presence of corals and other forms of ancient life in these rocks, that 

 they could not have been accumulated in turbid waters, nor along lines 

 where argillaceous and siliceous materials were being deposited. An 

 entire or almost an entire cessation of these sediments must have taken 

 place before calcareous matter could accumulate in large quantities 

 along the same zones ; but in these instances, where the amount of 

 matter was insufficient, or the force of the current inadequate to trans- 

 port these materials far beyond the great zone of deposit, there would 

 be accumulated in the quiet waters the formations resulting from 

 animal exuviae ; and here only coidd we expect to find coralline lime- 

 stone and formations of similar character. 



In order, therefore, to have a clear idea of any portion of country, 

 it is necessary, in the first place, to take into consideration the mode 

 and manner of the original distribution of the sediments constituting 

 the series of formations ; for on this must depend their ultimate cha- 

 racter. The slow accumulations in one place, and the rapid accumula- 

 tion in another place, which we know to be necessary conditions of 

 geological deposition, must exert an influence, not alone on the charac- 

 ter and topography of the country, but upon the nature of its rocks 

 and its ultimate productions. 



