354 Descriptioti of a Natural Tu7inel. 



there had been no natural cavity in the rock, it is evident that 

 the stream would have been deflected from its line ; would have 

 followed the base of the hill, and have turned the extreme point. 

 We, therefore, without hesitation, refer the origin of this aque- 

 duct to an original cavity in the mountain, and highly approve 

 of the name of natural tunnel, which col. Long most appropriate- 

 ly has given to it. 



We have been led into these remarks chiefly from a desire to 

 draw the public attention to some conspicuous desiderata in the 

 geology of this country. No geological surveys having yet been 

 undertaken, our knowledge of the Apalachian mountains is very 

 limited. The ridges, independent hills, and vales, are very 

 numerous and diversified, and have not yet been geologically dis- 

 entangled from each other. We are consequently unable to say, 

 with confidence, where the mineralogical structure of the gold 

 region has its precise limits, or where the primary rocks termi- 

 nate, and the secondary begin. In truth, geologically speaking, 

 very little is known of the details of the Apalachian ridges, even 

 as it respects the place to which their rocks belong in the geologi- 

 ca:l series. Of some portions of them, it is true, we have some 

 information ; but among these we cannot include the south-west- 

 ern portion in the country of this natural tunnel. 



There is another very interesting branch, and as connected 

 with the Apalachian ridges, of great importance. Many have 

 considered them under their common designation of Allegheny 

 mountains, as the dividing line of the western and eastern rivers. 

 This is by no means so. The Susquehanna rises to the north be- 

 yond their area, and traverses obliquely their Pennsylvania ter- 

 minations, on its way to the coast. The Potomac pursues for a 

 while a north-east course, then turns to the east and penetrates 

 through the greater mass of those ridges, before it takes its regu- 

 lar south-east course ; and although the Rappahannock and 

 Roanoke may be said to descend from the eastern slope of the 

 Apalachians, yet the James river rises in their central parts, and 

 the great Kenhawa, which flows north-westward into the Ohio, 

 has its sources interlocking with those of the Roanoke. We want 

 not only the details from which to deduce the causes which have 

 governed the courses of these rivers, but proper data to reason 

 upon, for the cause of those interruptions of continuity in the 

 Apalachians, which have left so many knobs and hills, independ- 



