248 The Edinburgh New Philosophical Journal. 



glaciers polish the surfaces of the rocks over which they 

 pass, but this observation is not confirmed by M. De Luc. 



This number also contains another interesting paper by 

 the same author, on the transverse valleys or openings in 

 chains of mountains by which rivers escape, together with 

 an article by the late Professor Hoffmann on rivers which 

 break through mountain chains. M. De Luc alludes to 

 the erroneous supposition of a late traveller, who thought 

 the Indus and Sutledge the only two rivers in the world 

 which traverse gaps at right angles to the mountain-chains 

 in which they rise, and instances the Rhone, the Rhine, 

 the Danube, the Elbe, the rivers of Asia, Africa, and 

 America, as examples of a similar course. M. De Luc 

 alludes to the remark of Addison, who after observing the 

 source of the Rhone in the very heart of the Alps, and the 

 numerous clefts and rents by which it escapes, " could not 

 but think it has been guided by the particular hand of 

 Providence." The Elbe finds a deep passage of surprising 

 aspect through the mountains which divide Bohemia from 

 Saxony, the particulars of which are described by De Luc. 

 The Rhine crosses the Jura chain, between Mont Terrible 

 and the Foret Noire, where the mountains are almost per- 

 pendicular. Again the Rhine encounters the Eifel, a chain 

 of mountains through which it passes by a gorge. M. 

 Ami Boue states that the first narrow passage of the Danube 

 is a rent which cuts a mountain across, and in its course 

 passes several similar defiles called Les Portes de Fer, the 

 opposite sides of which all appear to correspond, as if they 

 had formerly been joined, and now merely broken by their 

 gaps. 



The Tigris issues from Diarbekir by a long defile, which 

 arrested the march of the Greeks under Zenophon from 

 the narrowness and steepness of the rocks. 



The Irtisch and Yenisei, two great rivers in Siberia, both 

 traverse a continuation of the lesser Altai chain. 



Burchell mentions six openings in mountain-chains which 



