786 THE JOURNAL OF GEOLOGY. 



former being the darker. The more important of the schist 

 areas have been given numbers from I to 38. An attempt has 

 been made to indicate the geological structure on the map by the 

 introduction of such of the important dip observations as the 

 scale of the map will allow, as well as small arrows which indicate 

 the inclination of the trough and crest-lines (pitch). The course 

 of an important fault is traced along the east bank of the Housa- 

 tonic River. 



GEOLOGICAL STRUCTURE OF THE AREA. 



Since the beginning of the study of the Green Mountains by 

 the Archean Division of the Survey, Professor Pumpelly has 

 emphasized the necessity of making careful observations of the 

 pitch of flexures, in order to arrive at a complete knowledge of 

 the geological structure. Observations of this character have 

 furnished the key to the structure within the area here studied. 

 The crest lines of the folds show considerable and frequently 

 changing inclinations, but the beds have withstood the stress to 

 which they have been subjected in this direction v/ithout disloca- 

 tion, as there is no evidence of any cross faults. The disturb- 

 ance which came from the east, and which developed the flex- 

 ures, has been so great as to overturn most of them, so that their 

 axes dip east, and locally to cause a disruption with the produc- 

 tion of rather steep thrusts of small displacement. An important 

 dislocation has occurred along the course of the Housatonic 

 River, which has carried the Canaan Dolomite over the newer 

 beds exposed west of the river. 



Structural features as shown i?i longitudinal sections. — A glance 

 at the map will show that all the important ridges, with the 

 exception of Barack M'Teth, Turnip Rock, and the Bear's Den, 

 are formed of the Riga Schist. The fact that these ridges 

 steadily increase in height in going southward, as well as the 

 tongue-shaped outline of the area, indicates that the general 

 pitch of the flexures is toward the north. This is in perfect 

 accord with the fact that the folds in the main part of the Mt. 

 Washington Mass have a northerly pitch. But although the 

 general pitch within the area now under consideration is north- 



