40 M. Andre Luc on the Openings in Mountain-Chains 



from top to bottom, and rising apparently a thousand feet, 

 present e , on either hand, a promontory of rocks and forests, 

 rising very abruptly, and forming a combination both grand 

 and beautiful. The passes of rivers through mountains are 

 almost invariably picturesque, and it is always interesting to 

 observe how faithfully the rivers explore the clefts in moun- 

 tain barriers, and, impelled by the power of gravity, Avind their 

 way through rocky defiles and pursue their continuing course 

 to the ocean. It is common to speak of such passes as being 

 formed by the rivers, Avhich are ofteii supposed to have burst 

 the barriers, and thus to have shaped their own channel. This 

 may have happened in some peculiar cases, and there are doubt- 

 less many instances where the lakes, of which many must 

 have been left at the retiring both of the primeval and of the 

 diluvial ocean, have worn or burst away their barriers, espe- 

 cially when composed, as they must often have been, of loose 

 materials. But, with respect to most rocky passes of rivers 

 through mountains, there appears no reason whatever to be- 

 lieve that the waters have torn asunder the solid strata ; a 

 more resistless energy must have been requisite for such an 

 effect, and we must therefore conclude that the rivers have, 

 in most instances, merely flowed on through the lowest and 

 least obstructed passages ; their channels they have doubtless" 

 deepened and modified, often to an astonishing degree, but 

 they have rarely formed them through solid rocks. Soon after 

 passing Lehighton, a little village three miles from Mauch 

 Chunk, we entered another pass, which the Lehigh makes 

 through mountains. It is not like the former, a section of 

 the barrier ; it is rather a long circuitous gorge between two 

 barriers, which, although they pursue a winding course, still 

 preserve their parallelism ; and their feet, near Mauch Chunk, 

 approach so near to each other, that there is only room for the 

 Lehigh and the canal on one side, and for a road cut into the 

 mountain on the other ; it is so narrow that the river is almost 

 within reach on the right, and the mountain-rocks are quite 

 so on the left." 



South America, — The Orinoco, at St Fernando de Ata- 

 bapo, turns all at once to the north, and passes a chain of 



