36 IVI. Anclie de Luc on the Openi)i<^s in Moiintain-Chains 



very smooth in Hungary, because flowing through a very flat 

 country ; but among the mountains ol* Bannat and Servia, 

 where it is considerably confined, it acquires a fearful rapidity, 

 which, in connection with the shoals occurring here and there, 

 renders its navigation extremely dangerous. 



M. Ami Boue states that the first narrow passage of the 

 Danube is a rent which cuts a mountain across. Lower, the 

 river runs through a second contraction, where its bed presents 

 a series of rocks and rapids. At the first defile, the banks of 

 the river are so steep that there would be much difficulty in 

 making a road ; the road at present passes over the mountain. 

 These narrow passages are called Les Fortes de Fer. M. 

 Lippy, a naturalist quoted by D' Aubuisson, Avas struck with the 

 coiTespondence of the beds on the different sides of the pas- 

 sage ; all appeared to him to indicate the former junction of 

 the two chains now separated by these Fortes. 



Mr Lyell, in his Frinciples of Geology, remarks, that in the 

 south-east portion of England, the draining off" of the waters 

 is not effected by rivers which follow the great valleys exca- 

 vated in the argillaceous beds, but by valleys which run in a 

 transverse direction, passing across the chalk to enter the ba- 

 sin of the Thames on the one side, and the Channel on the 

 other. Li this manner, the chain of chalk hills in the north 

 is cut asunder by the rivers AVey, Mole, Darent, Medway, and 

 Stour ; and those of the south, by the Arun, Adur, Ouse, and 

 Cuckmere.* If these transverse openings were filled up, all 

 these rivers would be forced to turn to the east, and flow into 

 the sea, in the counties of Sussex and Kent. 



Asia. — In western Asia, the country of Diarbekir presents 

 us with an example similar to that of the Elbe, of a river 

 flowing from a girdle of moimtains by a narrow defile. Diar- 

 bekir is a country of an elliptical form, surrounded by moun- 

 tains, and intersected by upwards of eight rivers, which unite 

 in the Tigris. This river issues by a long defile, bordered with 

 very high rocks, which do not admit of a passage for travel- 



* Considering the limited extent of the country, these rivers, compared 

 Tcith those of Europe, may be regarded as mere rivulets. 



