﻿Geology and Mineralogy. 237 



tion has been answered, but not directly, in my paper of June, 1885, 

 In view of the enquiry since made I here state the differences. 

 In Scotland, gneissic and other crystalline rocks, through a 

 length from north to south of 90 miles, were carried westward 

 ten°miles over scarcely crystalline f ossiliferous Silurian rocks, and 

 effects of the friction were visible in the production of meta- 

 morphic schists at the contact and in other ways. In Berkshire 

 the facts are as follows: 



While the region is one of numerous north and south over- 

 thrust folds, with the thrust westward, there is no evidence in 

 the positions of the rocks, abrasions, or in any other way, of a 

 general overthrust. 



The rocks within the limits laid down by Emmons are, in most 

 of its cross sections, beginning on the west in eastern New York, 

 as follows : (1) Glossy hydromica schist, resembling glossy roof- 

 ing slate. (2) Feebly crystalline gray to grayish white lime- 

 stone. (3) Hydromica slates, slightly coarser than (1) and usually 

 somewhat chloritic. (4) Limestone less feebly crystalline than 

 (2). (5) Hydromica schist of the Taconic Range, somewhat 

 coarser than (3) and commonly more chloritic, and less coarse on 

 the western side of the belt than on the eastern, and along the 

 latter sometimes garnetiferous. (6) Coarse crystalline limestones 

 including white to gray marble. (7) Mica schists, often garnet- 

 iferous, graduating into and interlaminated at times with quartz- 

 yte. (3) Coarsely crystalline limestones, marbles. (9) In some 

 parts, quartzyte which is at times interlaminated with mica 

 schist. (10) Gneiss, mica schist, hornblendic gneiss, etc. In 

 southern Berkshire, as a consequence of the general fact that the 

 metamorphism is greatest to the south, No. (5) is a chloritic hy- 

 dromica schist, in places somewhat garnetiferous, on the west side, 

 and mica schist, garnetiferous and staiirolitic on the east side, the 

 two sides four to five miles apart. 



The nine belts consist alternately of limestone and schist, with 

 quartzyte at the east, 2, 4, 6, 8 being limestones. They vary in 

 width from a fourth of a mile or less to three or four miles or 

 more ; and the whole width of the north and south Taconic for- 

 mation in the section is about twenty-five miles. The dip of all 

 the strata is in general eastward and conformable. 



If, now, the eastern rocks had been thrust westward over the 

 western, or the western over the eastern, it would be plainly 

 manifest. There is not a shadow of evidence in favor of the idea. 



The fossils that have been found within the Taconic system 

 occur in the limestones (2) and (4) just west of the Taconic 

 Range. There is no mica schist within ten miles of them, and 

 the nearest gneiss is 20 miles off. The limestone and the asso- 

 ciated hydromica schists are alike in grade of metamorphism, 

 both being feebly crystalline. 



Four limestone belts are mentioned in the cross section ; but 

 in other sections there are only two, and in others five. The 



* This Journal, III, xxix, 441. 



