504 Notes on the Pyrenees. 



the Andes to the culminating points of the Pyrenees, and hi 

 the Himmaleh to the culminating points of the Alps. From 

 considerations founded on the same data, the relation of the 

 mean height of minimum of crest to the culminating point 

 would be in the Pyrenees as 1 : 1 '^ ; in the Alps as 1 : 2 ; in 

 the Andes as 1 : 1 '8 ; in the Venezuela as 1 : 1 '8 ; in the Cau- 

 casus as 1 : 2 ; in the Alleghani as 1 : 1*8 ; in the Himmaleh 

 as 1 : 1-8. 



Considerations founded on a physical conception of the 

 height of chains, which will improve as the facts connected 

 with their physical laws will be more perfectly developed, 

 are of the highest interest to the oryctography of the earth. 

 The graphic sections used by De Humboldt in his delinea- 

 tions of the Andes, by Parrat and Engelhardt in the Cau- 

 casus, by Wahlenberg in the Alps of Switzerland and the 

 Carpathians, by Schublers and Hoffmann in France, by 

 D'CEynhausen and Deehen in the Capitania de Minas 

 Geraes, by D'Eschwege in the plains of Mysore and the 

 gates of Malabar, and by the engineering officers attached 

 to the survey of Major Lambton in India, and which are 

 founded on simple barometric or geodesical operations, have 

 been of much utility in obtaining conclusions of this nature. 

 The Marquis La Place, led to consider that the surface of 

 the earth, when liquid, would be pretty nearly in a state of 

 equilibrium, from the harmony which experiments on the 

 pendulum offer with the results given by the mensuration of 

 terrestrial degrees and with the lunar inequalities, remarks, 

 that as it would follow from this agreement that the mean depths 

 of the sea might be of the same nature as the height of con- 

 tinents and islands, it must be evident that the mean height 

 bears little connection with the culminating points of moun- 

 tain chains, while the mean height of the crests forms an indis- 

 pensable accessary to the evaluation ; and, as De Flumboldt 

 has remarked at greater length, the chains and mountains 

 which attract the curiosity of the vulgar have much less 

 importance in such considerations than the vast plateaux, and 

 undulating plains, and alternating slopes, which influence, by 

 their extent and their mass, the position of the mean surface ; 

 that is to say, upon the height of a plane so placed, that the 

 sum of the positive ordinates are equal to the sum of the 

 negative ordinates. 



There are other more or less important phenomena 

 attached to the geography of mountain chains, and among 

 these their external aspect and outline form interesting fea- 

 tures, when from the ramparts of Montauban we first com- 

 mand that vale, or rather plain, which extends on one side to 



