DORSET VALLEY. 115 



duced this gulf, is made exceedingly improbable by the tortuousness of its course, 

 which would prevent the action of waves, and would be followed by no volcanic 

 rent. It corresponds, however, to the known effects of currents of water, when a 

 country is undergoing drainage. 



I might perhaps consider the gorge of the Rhine as commencing as far down as 

 the Drachenfels, and extending even to Mayence. But the valley is a good deal 

 wider at these extremities, and I prefer to confine this example to that portion of 

 it which seems unequivocally the work of river action. 



The strata cross the Rhine nearly at right angles, and appeared to me, from 

 the steamboat, to dip 60° to 70° S. easterly. 



19. Valley of erosion in Dorset, Vermont. — Those who have passed from Man- 

 chester to Rutland, in Vermont, on the Western Vermont railroad, will not forget 

 how narrow the valley is, especially in Dorset and Danby. Its east side is formed 

 by the Green Mountains, and its west side by a ridge not so high, which at its 

 southern extremity has received the name of Dorset Mountain. Near the base of 

 Dorset mountain the Otter creek takes its rise, and runs northerly into Lake Cham- 

 plain, at Vergennes. Near the same spot rises the Battenkill, which runs south- 

 westerly and empties into the Hudson at Greenwich. Both these streams are 

 mere brooks at the base of Dorset mountain, and the idea that they ever wore out 

 the valley in which they run, is quite absurd, especially as they flow in opposite 

 directions. Dorset mountain, according to the careful measurements of Mr. W. A. 

 Burnham, teacher in Burr Seminary, in Manchester, is 1627 feet above the valley, 

 whose summit-level must be near the base of the mountain. This is, however, a 

 valley of erosion; for near the top of Dorset mountain is a thick bed of white 

 limestone, which is interstratified with a metamorphic talcose slate, sometimes 

 called the Taconic slate. The mountain rises very precipitously from the valley, 

 being almost perpendicular on its east side, and in the limestone, not far from 1600 

 feet above the valley, is a cavern opening towards the valley, and sloping towards 

 the west, as represented in Plate XII. fig. 5. On exploring this cavern for several 

 rods, I met with unequivocal evidence that it had been formed by running water. 

 I traced it several rods into the mountain, and think it may be followed much 

 further. 



Now the conclusion is a legitimate one that a stream of water of considerable 

 size once, and for a long time, ran through this opening. Consequently the valley 

 east of it must have been filled to the height of the stream, in order to form a sur- 

 face for a river bed. Consequently the valley, 1600 feet deep, and many miles 

 long, must have been excavated since that period ; for I saw no evidence of any 

 upheaval of this mountain at a subsequent date. 



What agencies were concerned in this work, it may be difficult fully to under- 

 stand. It is certain that existing streams have not produced it. Drift agency, 

 while the continent was beneath the ocean, may have had some effect ; as, also, 

 the slow action of the waves during the vertical movements of the land. But the 

 length, narrowness, and depth of the valley, and the steepness of its sides, agree 

 better with river action, and I cannot doubt that the work was mainly accomplished 

 by that agency on some continent long, long anterior to the present. 



