Notes on the Pyrenees, 505 



lateral chains, is generally marked by an increase of elevation 

 (culminating point) ; as the extremity of these branches, when 

 not lost in the plain, is generally a peak of considerable 

 height. 



The culminating points of lateral chains may surpass in 

 height the elevation of the summits of the principal chain, 

 while the mean height of the crest of the latter is greater than 

 that of the former ; as the height of the culminating points in 

 one chain of mountains may exceed that of another, while 

 the mean height of the crest may be greater in the latter : 

 and this is the groundwork of the greatest difference between 

 the Alps of Switzerland and the Pyrenean mountains. 



Superiority of height of crest, as well as preeminence of 

 summit, may also exist in parallel or in transverse chains, and 

 not in the principal ; and as a general fact, not hitherto ob- 

 served, the culminating points of countries of mountains are 

 seldom in the centre of the chain, but at the extremity, whilst, 

 when the highest summits occur towards the centre, they 

 almost invariably exist in small transverse branches, and some- 

 times between two parallel chains. It must not be confounded 

 here that transverse chains may be parallel to one another 

 while at right angles to the line of the crest ; they are then 

 parallel transverse chains, but not lateral, and the structure 

 of the ridges most generally differs from that of the lateral 

 chains. The same may be observed of the latter when op- 

 posed to the principal crest ; but when the last is wanting, 

 and the crest exists in a series of parallel ranges, the struc- 

 ture will be found similar, or, at least, pretty nearly of the 

 same age. 



The culminating points, or the maxima of the lines of the 

 crests of the principal chains of mountains in Europe, in Ame- 

 rica, and in Asia, are, according to De Humboldt, as the 

 numbers 10, 14, 18; that is to say, they follow pretty nearly 

 a progression by differences, whose relation is one half. But 

 in the seven chains of the Alps, the Andes, the Himmaleh, 

 the Caucasus, the Alleghani, and the Venezuela, the relation 

 between the mean height of the crest and the culminating 

 points is as 1 to if^, or as 1 to 2. 



M. Ramond had already remarked, that the crest of the 

 Pyrenees is only a little lower than the mean height of the 

 Alps, while that which characterises the last chain is the great 

 relative elevation of its culminating points ; that is to say, the 

 relation of these summits to the mean height of the line of the 

 crest. From De Humboldt's calculation, founded upon the 

 mean height of the passes or ports, and that of the culmin- 

 ating points, the mean height of the line of crest is equal in 



