52 Baron Humboldt on Rock Formations. 
be se] -arated in the most distinct manner from the oolitic lime- 
stone beds ; while in Switzerland, in Germany, and in South 
America, they have for equivalents beds of marls subordinate to 
the Jura limestone The gypsums, which, in one district, are 
sometimes only intercalated beds in the alpine limestone or ooli- 
tic sandstone, in another district, assume all the appearance of 
independent formations, and occur interposed between the alpine 
limestone and the oolitic sandstone, betw^een this sandstone and 
the muschelkalk. The learned Oxford Professor, Mr Buckland, 
Avhose extensive researches have been equally useful to the geo- 
gnosts of England and of the Continent, has lately published a 
table of parallel formations, or, as he calls them, equivalents of 
rocks, which only extends from the 44th to the 54th degree of 
north latitude, but which merits the greatest attention. (0?i the 
Structure of the Alps, and their relation with the rocks of Eng- 
land, 1821.) 
As in the history of ancient nations, it is easier to verify the 
series of events in each country, than to determine their mutual 
coincidence; so also more accuracy can be attained in estima- 
ting the superposition of formations in isolated regions, than in 
determining the relative age or parallelism of formations which 
belong to different systems of rocks. Even in countries which 
are not widely separated, in France, in Switzerland, and in Ger- 
many, it is not easy to fix the relative antiquity of the muschel- 
kalk, of the molasse of Argovie, and of the quadersandstein of 
the Plartz ; because rocks of general occurrence are here most 
commonly wanting, which, according to the happy expression of 
of M. de Griiner, serve as a geognostical horizon, and with 
which we might compare the three formations in question. 
When rocks are not in immediate contact, we can only judge of 
their parallelism by the relations of age existing between them 
and other formations by which they are united. 
These inquiries of comparative geognosy, will long occu- 
py the sagacity of observers ; and it is not surprising that those 
who set out with the idea of retracing each formation in all the 
individuality gJ* its relative position, interior structure and subor- 
dinate beds, should finish with utterly denying all analogy of 
superposition. 1 had the advantage of visiting, previous to my 
journey to the Equator, a great part of Germany, of France, of 
