112 ON EROSIONS OP THE EARTH'S SURFACE. 



ance : one is the canal leading from the coal mines of northern Pennsylvania; the 

 other, the Erie railroad : both cut out of rock in many places, and overhung as it 

 were by ragged precipices. It is impossible to ascertain the depth eroded by the 

 river, because the banks are so irregular. Near the lower end, however, it is 

 obvious that Mount Butler, on the New York side of the river, once constituted 

 the barrier that has been cut through. It is 750 feet above the river at its base, 

 and I thought I discovered traces of river action nearly all the way upwards on its 

 steep face, and in some places on the top, although drift striae are found in some 

 prominent places. From Narrowsburg to Port Jervis the river descends, according 

 to the aneroid barometer, 215 feet ; so that if the barrier was once closed as high 

 as Mount Butler, a narrow lake must have reached much further than Narrows- 

 burg. 



The course of the stream through this gorge is quite crooked. Of course it has 

 been thrown with great power against particular spots and worn them away more 

 rapidly, so as to form flats on the opposite side. In such cases these flats are 

 almost invariably occupied by terraces of rather coarse pavel and considerable 

 elevation. The serpentine course of the stream precludes the idea of the ocean's 

 having worn out the gorge to any great extent. 



8. The Grand Canon on Canadian River, in (lie country of the Camanche Indians. 

 The southwestern portion of the United States, this side of the Rocky Mount- 

 ains, is remarkable for the numerous deep gulfs through which the rivers run. 

 These are called Canons. Often they occur in a level region, where the strata, 

 usually sandstone, lie nearly horizontal. In such a case the traveller, as he passes 

 over the plain, sees no signs of a river till he finds himself suddenly stopped by a 

 wulf, it may be several hundred feet deep, with walls nearly perpendicular, and 

 sometimes for a day or two may he travel along the stream, unable to find a spot 

 where he or his animals can get to the water. He meets with another difficulty, 

 also, if he passes along the stream in the hope of finding a crossing place. When 

 he comes to a tributary stream, he will find most likely a canon, nearly as deep as 

 on the main river, and he will be forced to diverge along the tributary, till he can 

 find a passage over the gulf. Thus will he be compelled to deviate almost con- 

 tinually from his direct course, and moreover be tantalized by the sight of water 

 in the inaccessible gulf below him, while his animals are nearly perishing with 



thirst. 



I apprehend that travellers apply the term canon to mountain gorges as well as 

 the gulfs above described, and doubtless it would be proper to use the term in 

 describing eroded gorges in the northern parts of our country; certainly to such as 

 exist on the Niagara and Genesee rivers. But some of those described by officers 

 connected with the United States army, are of a depth and extent much greater 

 than any that have been mentioned. I shall give only a few examples, partly 

 because out of the many that have been described by travellers, the facts respecting 

 them are not given with sufficient definiteness to answer my purpose. 



Some writers do, indeed, speak of convulsions as the cause of these canons, just 

 as they do concerning the gulfs at Niagara and Portage. But the fact that they 

 exist along the tributaries, as well as the main stream, shows that they are the 



