C. L. Whittle — Main Axis of the Green Mountains. 347 



Art. XXXVII. — The General Structure of the Main Axis of 

 the Green Mountains ; by Charles Livy Whittle. 



[Published by permission of the Director of the United States Geological Survey.] 



The anticlinal nature of the main axis of the Green Moun- 

 tains was first suggested by Adams in 1846.* In 1847 the 

 elder Hitchcock published a section of Hoosac Mountain in 

 Massachusetts representing the strata overturned to the west 

 and in his opinion the structure of the main axis in Yermont 

 was the same.f Zodack Thompson argued for a synclinal axis:j: 

 and T. S terry Hunt was of the same opinion.§ Edward Hitch- 

 cock in his Geology of Yermont represents the structure of 

 the axis between the Rutland and Plymouth valleys, along the 

 Central Yermont railroad as a simple anticline. |] At the time 

 this survey was made (1861) the subject of induced schistosity 

 was in its infancy, and it is rather surprising that the strati- 

 graphy worked out so largely on the basis of schistosity alone 

 should so nearly approximate to the real attitude of the very 

 varied terranes that make up the area of the Green Mountains. 

 Hitchcock's section YI, twenty miles north of section Y, makes 

 the gneiss dip uniformly east. Although along these lines the 

 gneiss is represented as having a simple structure the text 

 mentions that there are many minor irregularities and curvings 

 in the stratification especially along the southern line near the 

 town of Mt. Holly. The method then prosecuted of making 

 geological maps by crossing the state once in so many miles, 

 making observations on strike and dip where possible, accounts 

 in part for the disagreement in the interpretation of the 

 structure along the two lines mentioned. 



My own observations in Yermont made mainly during 

 three field seasons extended north and south along the highest 

 portions of the Green Mountains from Chittenden on the 

 north to Stratton on the south, and defined on the east and 

 west by Windsor and Rutland valleys. 



This area comprises part of the stretch of country em- 

 braced by sections Y and YI above mentioned in Rutland 

 and Windsor Counties. 



* Second Annual Report on the Geology of Vermont. Adams. 1846, pp. 167 

 and 168. 



f Hlementary Geology. E. Hitchcock. 1847, p. 36 and 37. 



\ Address on tne Natural History of Vermont. Preliminary Report on the 

 Natural History of Vermont. Augustus Young. 1856. A pp. 6, pp. 65-68. 



§ On Some Points in the Geologv of Vermont. This Journal, vol. xlvi, 1868, 

 p 229. 



|See vol. ii, Sec. V, 186], and text giving description of this section, pp. 

 624-628. 



