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former being the darker. The more important of the schist areas have been given numbers from 1 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 Housatonic River.

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 without dislocation, as there is no evidence of any cross faults. The disturbance which came from the east, and which developed the flexures, has been so great as to overturn most of them, so that their axes dip east, and locally to cause a disruption with the production 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 in 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-