496 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



The tides of this bay were on a scale which for a bay of this width 

 have no counterpart at the present time. They passed strongly up the 

 Avest side and down the east side, and were here reenforced by the prevail- 

 ing west winds, so that they formed very coarse conglomerates on the east. 

 The currents sweeping up the west side, past shores and over bottoms of 

 coarse and deeply decomposed granites, swept granitic debris far north, over 

 the area of black schists. Those passing south swept argillite and quartzite 

 debris far south along the pegmatite shore-line of the east side, and the peg- 

 matite material south along the tonalite and schist teiTane, and only where 

 the bay widened Avas there in its center an elaboration of quartz sand to 

 form the brownstones. In the narrower \rAYts of the bay the two shore con- 

 glomerates meet along a central suture, so to speak, and this ends so abruptly 

 at the north end of the basin as to suggest that it extended much farther 

 north and was perhajis a strait opening into a larger area to the north. 



The network of faults which bounds and intersects this basin permitted 

 the sinking of its bottom, in which movement the block from Amherst to 

 Northfield participated in a much less degree than did the rest. In the 

 great transgression which followed, the waters slowly rose upon the bottom 

 and the slopes of the basin and found a great abundance of material ready 

 for transportation and redistribution, because the rocks had become deeply 

 disintegrated during the long period of emergence which was now brought 

 to a close. 



I have examined both shores of the Bay of Fundy as well as the 

 fiords of Norway and Scotland, and in comparison the work done here 

 seems to me to indicate stronger cun-ents, a larger amount of material, 

 more rapid change of level of the sea, and more rapid deposition, than can 

 be found in any modem examples. The sea seems to have risen over the 

 flats and slopes of deeply softened rock more rapidly than it could remove 

 the material, and therefore advanced without foi-ming a fixed and deep-cut 

 coast line. It often moved the softened debris in such large quantity to its 

 present resting place that it is scarcely sorted or rounded even when quite 

 coarse gravel. Indeed, the study of this Triassic transgression has tlu-owu 

 more light upon the ancient and more widespread Cambrian transgression 

 (Chapter V) than I have gained from the examination of more modern 

 instances. 



It is very remarkable how entirely the finest clayey material was 



