64 NEW YORK STATE MUSEUM 



structure of its type known. The wide departure of its axes from 

 the formation trend is believed to point to at least two periods of 

 orographic disturbance in this vicinity. 



Igneous rocks are ordinarily in the form of sills. In the case 

 of the gabbro these may represent stocks or bosses rolled out by 

 dynamic readjustments, but many of the smaller masses were un- 

 doubtedly intruded as thin sheets to form an injection zone, such 

 as that south of Pierrepont. In the case of the granite, the habit 

 is much the same ; but the sills are of huge dimensions and together 

 with the smaller bosses probably represent the irregular surface of 

 a regional bathylith. 



In view of the limited area covered by the field work for this 

 report, perhaps too much reliance should not be placed upon the 

 broad generalizations here offered. Nevertheless they represent, 

 in the writer's opinion, the weight of evidence for this quadrangle; 

 but they are recognized as being subject to modification when 

 viewed in the light of future more extended researches. 



Professor Chadwick, who has been engaged with the Paleozoic 

 rocks of this quadrangle, reports as follows: 



The Paleozoic formations occupy the northern third of the quad- 

 rangle and occur also as several small outliers through the southern 

 half. The northern outcrops are in general quite limited in number 

 and in area, since the region is under a heavy cover of drumlin 

 drift; they are confined chiefly to the beds of the Grasse river, 

 Trout and Stony brooks, and the Raquette. While all the layers 

 decline, broadly speaking, to the northward, following the present 

 slope of the subsurface of Precambric crystallines, they present 

 many minor undulations of gentle dip, crisscrossing like the waves 

 of a choppy sea. 



Along the contact of the main mass with the crystalline rocks 

 that lie to the south, there exists a blank zone exceeding 13/2 miles 

 in breadth, in which bedrock is wholly concealed. The first out- 

 crops seen on the north of this zone are small, often easily over- 

 looked, exposures of the Theresa beds — upper semicalcareous 

 Cambric strata. These are followed, usually immediately, by ex- 

 tensive ledges of a white vitreous " quartzite," 20 feet or more in 

 thickness, containing numerous " Scolithus " and having much the 

 appearance of the " white Potsdam " sandstone, with which it has 

 evidently been confused in earlier explorations. Fine exposures 

 of this are seen at Morley and northeastward to the Trout brook, 

 thence southeastward along Stony brook to Sissonville on the 





