60 
THE GEOLOGIST. 
intrusion of older rocks^ the only variation being the existence 
of tertiary districts along the banks of the large rivers. The 
foundation of most of the level countries is generally limestone^, 
and the hills and ridges in some places consist of sandstone — a 
kind of dark coloured slaty clay^ containing vegetable impres- 
sions with a little mixture of carbon_, frequently alternates with 
all the strata of this formation_, the whole of which are nearly ho- 
rizontal. The highest mountains are on the external borders of 
the basin, gradually diminishing in height towards its centre. 
Two divisions of the secondary formation common in Europe 
have not been discovered in this ; the chalk formations_, and what 
Werner calls the "floetz trap/-* formation. The limestone found 
in this basin is of a bluish colour running through all the shades 
to a dingy black, having an even, rather earthy fracture, and 
sometimes a schistose structure. The flints found in the secon- 
dary limestone in America are generally black, resembling the 
Lydian stone, and in all kinds of irregular forms and branches^ 
intimately mixed with the limestone. The limestone, which 
often follows the chalk in countries when the latter formation 
occurs, is generally of a white, running into a drab or light 
brown colour, a smooth, compact, conchoidal, (almost resembling 
the flinty) structure, having in some parts of the stratum round- 
ed nodules of flint, interspersed apparently without order ; the 
flints in some places dark-coloured, in others light ; and some of 
the nodules whitish on the outer edge, and blackish towards the 
centre. 
A very extensive and regular formation of the above-men- 
tioned kind of limestone succeeds the chalk in Europe, and 
covers the transition formation on the north side of the moun- 
tains of the Crimea; holds, the same relative situation along the 
north side of the transition on the Carpathian mountains ; con- 
tinuing through Silesia and Bavaria along the Bohemian moun- 
tains to Ratisbon ; from thence up the Danube to Schaff"hauseu 
on the Bhinc; and follows the north-west side of the Jura, 
