SOME RIVERS OF CONNECTICUT. 



387 



to work against this obstacle, abstracted its head waters and the 

 gap was abandoned. The accompanying diagrams may make 

 this easier to understand. Figure 2 is a cross-section of the 

 faulted monocline, R showing the position of the river along the 

 foot of the fault cliff. The line B L represents the surface of 

 the country after baseleveling, the trap outerops forming low 

 hills (much exaggerated in the diagram). Figure 3 shows the 

 dislocated trap sheets, the fault line and the winding course of 

 the river, which has abandoned the fault line except where it 

 passes between the low trap hills. Here the country is at base- 

 level. Figure 4 represents the region after the elevation and 

 resulting erosion. The trap ridges have become more pro- 



FlGURES 2-4. 



nounced, and have migrated eastward in the direction of the 

 dip. The river has been slowly let down upon the northern one 

 from the sandstone at point G and has there cut into the solid 

 trap. 



The transverse notch of Cook's Gap, already described, 

 was probably located in a somewhat similar manner, but the case 

 is not so clear as at Tariffville. 



Gravel terraces of the Farmingtoii. A consideration of some 

 facts concerning the height and slope of the terraces along this 

 part of the river may give a clue to the answer to our question. 

 One-half a mile east of Tariffville and east of the trap ridge, the 

 highest terrace is 210 to 215 feet. Half a mile south of the 

 same place but west of the ridge the height is 275 feet. ^ The 



'J. D. Dana, Amer. Jour. Sci. 3d. ser., vol. xv, p. 506. 



