GEOLOGY OP THE VICINITY OF LITTLE FALLS 51 



Their great irregularity inay perhaps indicate that desiccation 

 was a prominent factor in their production. Of these rocks the 

 Utica shales show the most numerous and sharpest joints, and 

 they are least in evidence and most irregular in the Beekmantown 

 rocks. Three sets are often present in the Utica, because of 

 which the harder layers break out into triangular blocks. 



Though the fact can not be deduced from a comparison of the 

 readings, it is quite certain that the pre-Cambrian rocks were 

 jointed before the deposition of the paleozoics. The prevailing 

 east-west trend of the diabase dikes, in the regions where these 

 occur, would seein demonstrative of a set of joints having that 

 direction, and suggestive of the probability' that that was the 

 only good set. 



SOME OSCILLATIONS OF LEVEL DTJUING THE EARLY PALEOZOIC 



Certain matters which are in no sense novel call for considera- 

 tion here. The main propositions have been already advanced 

 by others. But the detailed study of the Little Falls district has 

 brought out evidence of the verity of certain notions long held 

 which is new, and also the facts can perhaps be marsha,led more 

 convincingly than has been the case hitherto. 



Paleozoic overlap on the pre-Cambrian floor 

 It has already been stated that in pre-Paleozoic times the 

 Adirondack region was a dry land area for a vast length of time, 

 and that a subsidence commenced during the Cambrian, in virtue 

 of which the sea slowly encroached on the region from all sides, 

 that it became an island in the midst of the sea, and that by the 

 close of the Lower Silurian the entire region was either entirely 

 submerged or else so nearly so that but little of it still protruded 

 above the waves; that, as it sank, each succeeding rock forma- 

 tion deposited on the floor of the encroaching sea, would extend 

 farther in on the old land surface than the previous one, so that 

 each would be in turn found resting on that surface in going 

 toward its center, constituting what is called overlap. This is 

 in the main the ordinary conception of this portion of the history 

 of the region, and has been specially elaborated by Mr C. D. Wal- 



