146 GEOLOGY OF THE SECOND DISTRICT. 



second is, the cooling of the great internal mass, by which change the external coat becomes 

 too large, and then in adapting itself to a diminished circumference, presses the strata late- 

 rally, so as to produce folds and wrinkles. Of the two views, preference is given to the first, 

 inasmuch as we have evidence that the phenomena of which I am speaking seem to have 

 taken place subsequent to the creation of aiiimals, and of course after the refrigeration of the 

 planet had reached its present state, or nearly so ; for there are reasons for the opinion that 

 it was not till after the deposition of the New-York system that the derangements occurred, and 

 which is particularly indicated by the direction of the uplifts and fractures in the Champlain 

 group, being parallel with those of the Taconic and Primary systems, and hence, according 

 to the views of distinguished geologists, occurred in the same era, if not at the same time. 

 Whatever may be the opinions on this point, it so happens that the direction of the uplifts 

 and fractures in the Primary, Taconic and New-York systems, are parallel, in those belts 

 which are immediately adjacent to each other. Tiierc is, it is true, an uplift with a fracture, 

 commencing near the western edge of the Taconic rocks, which runs up the valley of the 

 Mohawk, and which of course deviates considerably from parallelism with those which run 

 up the valley of the Hudson and Champlain. This appears to be an exception to what has 

 been stated, but the majority by far of the fractures are parallel with those valleys ; besides, 

 the era of that which produced the valley of the Mohawk, is probably much later. Before 

 these important questions can be settled satisfactorily, much labor in the field will be required. 

 Our country is so wide, the jioints for examination so numerous, and the whole field so ex- 

 tended, that some time must yet elapse before our doubts can be solved, and confidence given 

 to our speculations. 



There appears to be one point established by the phenomena of the rocks under considera- 

 tion : it is that sameness of dip and sameness in lithological characters, as well as other 

 points, may happen to two or more systems ; which leads me to remark, that where there are 

 resemblances of these kinds, we need not, for those reasons only, consider the rocks as at all 

 produced in the same era, or as belonging to one system ; for we know by observation, that the 

 same force which commences its action in an older s^^stem, may be extended to the newer, and 

 produce analogous effects. In most of those cases where similar derangements are produced, 

 we find the more marked effects at or near the junction of two rocks or systems, which un- 

 questionably arises from the thinness of the strata : a fact, too, which requires to be taken 

 into the account in estimating the thickness of a mass ; for along the exposed edges of frac- 

 tures, we may very probably ask ourselves if the same mass does not increase its thickness 

 towards the central part of its bed, or the deeper part of the basin in which it was deposited ? 

 However this may be, we often find, along the line of junction between difl^erent masses, nu- 

 merous fractures and uplifts, by which complicated derangements appear, and which create 

 many difficult points of inquiry that require an extended series of observation for solution. 



A question arises, whether the limestones which appear occupying distinct belts may not 

 in fact belong to one single bed, which was brought up by so many successive uplifts. Thus, 

 at the west base of the Taconic range, there is the sparry limestone ; passing over this range 

 to the east base, we find a bed also differing somewhat in lithological characters ; and passing 



