TACONIC SYSTEM. 139 



question is settled satisfactorily, may not the Taconic rocks be considered as simply the pri- 

 mary, and varieties merely of the talcose slates, primary limestone, etc. ? This question is one 

 of equal importance with the preceding, and requires an attentive examination ; and its decision 

 requires the establishment or admission of two or three doctrines or principles, which have 

 not been fully sanctioned by geologists, or recognized as authoritative. 



In fossiliferous rocks, geologists arc agreed to regard organjc remains as paramount to all 

 other characters, where the order of superposition cannot be determined by inspection. We 

 find, however, no fossils in the rocks of which I am speaking, and hence can derive no aid 

 from that source, upon which any reliance can be placed ; and besides, the peculiar posi- 

 tion in which they are placed adds difficulties to those already enumerated. But it is confi- 

 dently believed that there are characters which, though they may not give us that kind of 

 information which fossils do, yet are capable of being employed as distinguishing marks. 

 Those characters may be reduced to two principal kinds : 1 st, the lithological characters of 

 the rocks themselves, and which is the usual view taken of them ; and 2d, the imbedded or 

 associated minerals. As a general rule, certain minerals are found in particular rocks ; and 

 may not a similar rule or law prevail where a system of rocks is concerned ? 



But leaving this question for the present, I remark, that comparing the several members of 

 the Taconic system with rocks bearing the same name in the Primary, very little doubt 

 remains of their total dissimilarity. Comparing the slaty rocks of the former with the latter, 

 we find a broad fine of distinction drawn between them ; taking, for example, the so called 

 talcose slates of the two systems, I have no hesitation in saying that constant and reliable 

 differences exist, and may be found in all careful and close examinations. These differences 

 exist in the quality of the slates themselves, particularly in the color and lustre of the laminae, 

 and their peculiar contortions. But more decided diflerences are found in the associations of 

 the rocks : the talcose slate of the Prmiary system is universally associated with hornblende 

 or soapstone, or both ; while the talcose slate of the Taconic system is never associated or 

 connected with either of those rocks ; or, to state the fact in other words, never passes into 

 them, whereas in the former case it does. Another fact of the same nature is also well 

 determined by observation, viz. that the imbedded minerals belonging to each rock are 

 remarkably distinct. Actinolite, epidote, titanium, auriferous sulphuret of iron, etc. are never 

 found in the Taconic system. I might go on and state other particulars, or facts whose bear- 

 ing is the same, but this I deem unnecessary in this place. 



This brings us to the conclusion, then, that where the associated minerals are different, the 

 rocks themselves are different ; and there are so few exceptions to this statement, that it 

 appears to the writer to furnish sufficient grounds for separating one system from the other, 

 by the aid of characters sufficiently important and decisive for all the purposes of geology. 



I have confined my remarks to the diff'erences in the slates ; equally important are they, 

 when we compare the limestones of the other systems with those of the Taconic. While the 

 texture and grain of the limestones of the two systems differ, there are still more distinctive 

 and specific marks which may be employed : the presence of graphite in the limestones of 

 the Primary system may always be depended upon, even in hand specimens ; for not an in- 



