Notes on the Pyrenees. 508 
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 pr incipal 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 ef 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 
adden in the centre of the chain, but at the extremity, whilst, 
when the highest summits occur towards the centre, they 
almost iInvar iably 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 diier ences, 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 1-85, 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 
