216 



OEOLOGT OF THE THmO DISTRICT. 



In the instance of contortion given of the Trenton limestone, we had an example where the 

 force was within the mass ; here, one of lateral pressure upon very yielding materials, being 

 probably in a softer state than the contiguous undisturbed parts. These instances, so far, 

 afford us the only two known causes of contortion, plication, etc. of rocks ; and may explain 

 all the knovm cases of disturbance of like appearance, without resorting in any wise to forces 

 acting from below. In the rising and falling of great masses — and continents illustrate 

 such movements — a lateral pressure would result, forcing whatever soft or yielding mate- 

 rials were subjected to its power, to act upon themselves ; hence plications, contortions and 

 curvatures would be produced, like those of the clay beds of Black river, were the layers thin 

 and yielding to pressure. The same results would ensue, were a part of a mass subjected to 

 crystaUization, having insufficient space for expansion, or if unequally resisted by associates. 



Section exlettdif^ at a right angUfrom Black river, showing that the materials of tchich thehiUis composed came from tht 



direction of the river. 



No. 1. Apparently a mas* of yellow (and, forming the bank of the river. 



4. > Rolled stones of primary rock, limestone of Black river, and Trenton rock and sand with loam in No. 6. 

 6.) 



i^ > Sand same as No. 1. 



At the point where the feeder diverges from the river, there are alternations of rolled stones 

 of the largest size, and sand, rising apparently upon a mass of sand, the top of which is 

 about sixty feet above the river. The deposit of rolled stones and sand dip from the river at 

 a considerable angle, showing that the direction whence they came was from the part now 

 occupied by the valley or river depression on that side, the former showing no rise for a long 

 distance from the river. The alluvial hill rises one hundred or more feet in perpendicular 

 height above the river. 



The plain of Boonville, south of the village for some miles, and along the whole course of 

 the river to the mouth of the feeder, shows hills of alluvial ; rising about the same height as 

 along Black river, but more generally placed upon the Trenton limestone, which forms the 

 surface rock of that part of the country. 



