134 Scientific Geology. 



ington rivers. As may be seen on the map, these all cross a high 

 ridge of greenstone before they reach the Connecticut ; and in the 

 case of Deerfield river particularly, the gorge through which it pass- 

 es, not less than 250 feet deep, appears as if it must have been worn 

 down for the express purpose of suffering the river to pass. And 

 yet, this river has only to rise 80 or 90 feet above its present bed, in 

 order to find a direct passage to Connecticut river on the south side 

 of Sugar Loaf mountain. And so the Westfield and the Farmington 

 might have passed down the western part of the Connecticut valley, 

 and emptied at New HaveVi, had their beds been from 100 or 130 feet 

 higher than at present. And such must have been the course which 

 all these rivers would have taken, had not the gorges through which 

 they now pass in the greenstone ridges, been excavated for them be- 

 fore they began to flow, at least, to a considerable depth. 



The direction of the primary strata, and the general course of the 

 valleys in the mountainous region on the west side of the Connecticut 

 valley, is north and south. But instead of following these valleys, 

 Deerfield and Westfield rivers flow through ravines, running in gen- 

 eral across the strata, and across the general course of the valleys. 

 These ravines are, for the most part, very narrow and deep, and the 

 edges of the strata on their opposite sides correspond. It seems 

 difficult to suppose that these rivers have produced these ravines ; and 

 yet, since no similar ones occur in the region, one hesitates to say 

 that they were not formed by fluviatile action. There is not certainly 

 the same means of proving their existence previous to that of the 

 rivers, as in regard to the gorges already described, through which 

 these rivers and the Connecticut flow. Concerning the passage of 

 Farmington river through the primary regions, I am too ignorant to 

 be able to make any definite statements. 



Terraced Valleys. 



Although there is demonstrative evidence that the rivers under con- 

 sideration did not in all cases first excavate the valleys through which 

 they flow, yet there is on the other hand, evidence scarcely less con- 

 clusive, that they have considerably lowered their beds since they be- 

 gan to flow. Between the primary mountains, from whence Deer- 

 field and Westfield rivers, for example, issue, and the greenstone 

 ridges through which they pass, they have formed alluvial basins, 

 somewhat extensive, and sunk about 90 feet below the general level 

 of the bottom of the Connecticut basin. And the banks of these 



