62 NEW TOBK STATE MUSEUM 



the dikes around Lake Placid belong, we can not say from the 

 local evidence. 



As to what took place in this region in the long interval of time 

 represented by the paleozoic and mesozoic eras and the tertiary 

 period, we can but imagine and most imperfectly. Whether the 

 mountains were leveled off, submerged and buried under strata 

 that have since been removed, or whether they were a land 

 area, that suffered great denudation and furnished material for 

 later sediments, we have slight means of knowing. For the later 

 paleozoic and for the mesozoic and tertiary the latter supposition 

 is the more reasonable. Careful study of the physiography may 

 throw some light on the tertiary or even on the later mesozoic 

 times, if remnants of old drainage systems can be made out. Pre- 

 sumably their outlines were not so very different from the pres- 

 ent ones. 



At some time in this interval the great faults were developed 

 that have served to block out the individual mountains and val- 

 leys and that are the primary causes of the relief and of the 

 present drainage. The crushing of the rocks from the faulting 

 gave the rivers their easiest lines of erosion. This inference is 

 corroborated by the cracked and jointed condition of the rocks 

 in the channels, where exposed, and by the steep, precipitous 

 cliffs in the passes, which are due to- the scaling off of platy 

 masses along the old lines of fracture. These movements may 

 have occurred in quite recent geologic time, but in no case have 

 we found faulted glacial deposits. 



With the opening of the quaternary period came the invasion 

 of the continental glacier and the production of the moraines, 

 boulders and beautiful glacial amphitheaters or cirques on the 

 slopes of Whiteface and Sentinel. The boulders of Potsdam 

 sandstone indicate a movement from the northeast, and the few 

 glacial striae that have been met corroborate the inference. They 

 are not common in the area of the map and should be looked for 

 with care and their directions should be taken with a compass. 



The configuration of the mountain slopes is strikingly charac- 

 teristic of ice action, and if the reader will observe on the relief 



