GEOLOGY OP HAMILTON, WARREN AND WASHINGTON COUNTIES 14T 



in fault scarps, so that the valley is a depression dropped by fault- 

 ing below the general level, i. e. it is one of the " Graben " as the 

 term is used abroad. This appears to be certainly true for the 

 west side of the valley, where the gneisses go up in a fairly steep 

 wall, but it is less evident, though quite probable, for the east 

 side. Dr Ruedemann develops an argument against the concep- 

 tion set forth by the writer in the "Physiography of the Adiron- 

 dacks in the Cambrian and Ordovician periods" (cited above), that 

 the early paleozoic sediments set up into embayments and sub r 

 merged valleys in the subsiding archaean land area. The argu- 

 ment is based on the general similarity of the paleozoic beds at 

 Wells to those of the main areas along the south side of the moun- 

 tains; and on the general parallelism of the positions of the Wells 

 graptolites as they lie in the slates, to those in the Utica beds to 

 the south. Dr Ruedemann therefore infers a general mantle of 

 the paleozoics over the crystallines and their preservation in this 

 outlier by infaulting. As preliminary to farther discussiou of 

 this point, details of the Wells exposures will now be given. 



Potsdam sandstone. The Potsdam appears in largest ex- 

 posure just east of the Catholic church, but it is also revealed in a 

 pit, about 8 to 10 feet deep, immediately east of the hotel. At the 

 former locality 6 feet of thickness is exposed, but more lies below, 

 so that a total of at least 30 to 35 feet was inferred. The rock is a 

 tine grained, cream colored sandstone, rather thickly bedded, and 

 shows occasional tendencies toward conglomerate. Ripple-marks 

 are present. Under the microscope it appears as a quite pure 

 quartz sand, with grains about - 5 - - of an inch in diameter (.5 

 mm). The grains are all rounded in a very noticeable degree,. 

 and they must have been well triturated before deposition. They 

 are the common variety of quartz, as found in the ancient crystal- 

 lines. A little kaolinized and somewhat iron-stained feldspathic 

 material is also present. 



The exposure back of the hotel is very limited in extent, and 

 merely presents a fine, even grained and rather heavily bedded 

 sandstone, of whose thickness we have no means of knowing. Its 

 chief interest lies in the fact that it is flat and about 30' below the 



