104 DERANGEMENTS Of THE TACONIC SYSTEM. 



if they have been exposed to what is termed dlhivial action, and patches have been worn 

 or cut through, showing the lower rocks in the same strike. Now in a system as old as 

 the Taconic, we must admit its great liability to be deranged, and its members to be 

 champed in various ways ; in ways as numerous as the physical agents themselves, fire, 

 water, frost, abrasions, disintegration, etc. It is therefore really to be expected that diffi- 

 culties should occur in the adjustment of its members ; but these by no means appear 

 insurmountable, when we are once in possession of all the facts relating to the system. 



The doctrine which I wish to inculcate in the preceding remarks, is, that a system of 

 rocks may be rendered obscure by a parallel division of its beds, or by a parallel separa- 

 tion of its individual members : they may be so divided as to be worn out by the agents or 

 powers of nature, or become insignificant, or separated so far asunder as to be lost sight of; 

 and the older any system is, the more liable is it to suffer by these accidents. The Taconic 

 system has especially suffered by these causes ; and in consequence of its proximity to other 

 systems and rocks probably of a similar origin, many perplexing questions arise, of which 

 other systems are entirely free. 



In studying the rocks of this or any other system, I select those districts where there is 

 the least disturbance. By this course, I am enabled to learn, not only what the members 

 of the system are, but also their true order of succession. In this system, I have particu- 

 larly examined the district marked out at the head of this article, as it is here that few if 

 any intrusive rocks of any kind occur ; and I find a certain number of them lying in 

 parallel bands, which on both sides, tlie east and west, prove unconformable to the two 

 systems lying one above the eastern system of schists, and the other below the shales that 

 constitute a part of the western system, the New-York or Silurian. 



Now wherever I find these members, although they may be separated from each other 

 as they are at the Highlands, I am determined still to call them by their right names ; 

 though I am ready to express my fears that some of my favorite bantlings have been so 

 mucii altered in some localities, that I may fail to recognize them. I suspect, too, that it 

 may liappen in some cases that only the fragments of the system have come down to us, 

 80 that it will be impossible to bring together the remnants in such a condition as to make 

 even a tolerable appearance on a map. 



I have only a few more words to say in this connection, namely, that the difficulties 

 attending the adjustment of the rocks of the Taconic system cannot be appreciated without 

 a tolerable knowledge of the characters of all the rocks with which they lie in juxtaposi- 

 tion. Very little embarrassment is occasioned by the presence of gneiss or mica slate near 

 any of the members of the New-York system, so far at least as to distinguish one from 

 the other ; but not so with the rocks under consideration, for reasons which I have already 

 given. 



