Structure of the Eastern Alps. 333 



ciations of sandstone (sometimes passing into chert and sometimes containing 

 green grains) with the fucoid grits and shales*. 



This fact ahnost demonstrates^ that the largest portion of the fucoid shales, 

 are subordinate to the green-sand series. According to M. Adolphe Brongniart^ 

 fucoids are highly characteristic of the green-sand and cretaceous periods ; 

 and from our own observations in the Eastern Alps^ we are disposed to sub- 

 scribe to that opinion : for in these youngest, secondary groups of the chain, 

 we have never detected the trace of any of those vegetables, which are consi- 

 dered more peculiar to the oolitic series; nor, on the other hand_, has the Alpine 

 limestone afforded us a single specimen of a fucoid. By combining these positive 

 and negative facts with the evidence derived from the order of superposition, 

 we are induced, as is stated in the previous chapter, to place the fucoid strata 

 near the base of the green-sand series. This is, at least, as perfect an arrange- 

 ment, as our present knowledge enables us to venture upon ; a more minute 

 acquaintance with the fossil history of the Alps, may hereafter lead geologists 

 to a better defined subdivision of these groups. 



It will be seen from the section f , that the green-sand ridges on the left 

 bank of the Iller, to the north of Ober Mieselstein, have all a northerly dip ; 

 but in the neighbourhood of that place the beds dip in every direction, and 

 appear at almost every angle of inclination. Breaks and contortions are found 

 in all parts of the calcareous chain, but can seldom be referred to any visible, 

 disturbing cause. In this instance we are however more fortunate ; for in 

 the gorge of the Schinberger-Ach several large dykes of basaltic green-stone, 

 are seen to rise to the height of forty or fifty feet up the abrupt face of the 

 mountain, and there to terminate in wedge-shaped masses ; which, from the 

 effects they have produced, and their manner of association with the tilted 

 beds of limestone and green sandstone, offer the clearest proofs of their forcible 

 protrusion J. The rocks in contact with the trap are hardened and altered ; 

 and some of the green-sand beds are almost reduced to a compact state, and 

 from being traversed by joints or fissures separate into prismatic masses. In- 

 deed there is, here and there, so apparent an admixture of the stratified and 

 the igneous rocks, that we could with difficulty draw a line of separation be- 

 tween them. The strata are highly inclined and nearly vertical in the lowest 

 part of the gorge, where they are associated with the basalt; and the over- 

 lying calcareous masses of the Schwarzenberg, to which it has not penetrated, 



* This sandstone is much quarried as a building stone, and in several places cannot be distin. 

 guishcd from the quader-sandstein (grcen.sand) of tlie north of Germany. 

 t Plate XXXVI. fig. 4. 

 X Our attention was called to these dykes by M. Betterich, % venerable pastor of Mieselstein. 



