eO RELATIONS OF THE TACONIC SYSTEM. 



The section in the margin exhibits the con- 

 '^' * nection of the quartz and primary schists, with 



which, however, there are beds of granite 

 containing a peculiar blue quartz, that enters 

 also into the composition of the breccia already 

 referred to ; and I may add that I observed 



a. Brown sandstone or granular quartz ; b. Gneiss with beds of gra- 

 nite, in which quartz predominates ; c. Thick beds of drift, this at Adams (Massachusetts), nearly forty 



miles further south. 



I have now stated the facts in regard to the junction of the Taconic system, first, on the 

 west with the New-York or Silurian system ; and secondly, on the east with the Primary 

 schists, with which it is also unconformable. From the preceding account, it is not to be 

 doubted but that there is a system of rocks lying, as has been heretofore maintained, 

 between Hoosic mountain range and the Hudson river, of an age posterior to the gneiss 

 and mica slate, and anterior to the New- York system. It consists, throughout all its beds, 

 of sedimentary matter generally in a state of fine division. These beds are conformable 

 to each other, and arranged in uninterrupted succession, although their lithological charac- 

 ters are very diverse. 



These facts, therefore, go to show the unity of the rocks which compose the Taconic 

 system ; being deposited during a greatly extended period, which will be shown to have 

 abounded in part in organic bodies, whose forms were as remarkable as any in the animal 

 kingdom. 



From considerations which have been adduced in this section, the doctrine of metaraor- 

 phism is of no consequence. We may admit the fact, without involving the question of 

 age, either in one or both systems : each may have undergone great changes in mechanical 

 texture, without embarrassing our conclusions, even though two limestones, slates or sand- 

 stones become by those changes identical in lithological features or composition. 



I have already stated that the Taconic system lies between the Hoosic moimtain range 

 on the east, and Hudson river on the west: I may now add that it embraces a belt of country 

 at least forty miles wide. Tliis statement is confirmed by my researches since the Report 

 on the Second District was published, its extent being increased by an extension of the 

 Taconic slate beyond those limits which I had then fixed upon. In this ancient system, 

 contrary to what would be expected, perhaps, we find as few disturljances as during any 

 other subsequent periods ; that is, in the belt of country between the Hudson at Albany and 

 the Hoosic mountain, no remarkable ones seem to have occurred, except that by which 

 the rocks have been thrown into an inclined position : there are no intrusions of igneous 

 rocks, as dykes, beds of granite, etc. ; though when we trace the system south, distur- 

 bances are quite common ; but even in the midst of them, I may say that the metamor- 

 phisms are no greater than in many rocks of a much later date. So that the eflfects of 

 intruded igneous rocks are not always strongly manifested ; and, in fact, in New-York, 

 they are scarcely worthy of aticnlion, unless indeed for the very point stated, the extremely 

 slight change that appears just at the junction of the two rocks, and then the alteration 



