396 Professor Sedgwick and Mr. Murchison on the 



sand, probably derived from the degradation of the surrounding deposits, is 

 spread out from the left bank of the Mur, to the southern edge of several lofty, 

 serrated ridges of volcanic rocks. Our line of section passes through some of 

 the finest of these volcanic masses, in its range from Hainfeld, on the Raab, 

 through Gleichenberg, to Straden : and had it been drawn a little further to 

 the east, it would have passed over a volcanic ridge stretching southward as 

 far as Klech. 



By skirting these volcanic ridges on their western side, we were led along a 

 succession of hills, of the youngest tertiary marine deposits ; in some places 

 offering clear, uninterrupted sections ; in others, alternating with, or overlaid 

 by, different varieties of the contiguous igneous rocks. At Straden, a hill rises 

 several hundred feet above the plain. It is composed towards its base of cal- 

 careous shelly sands, which pass upwards into compacted conglomerates, of 

 well-rounded pebbles, the beds of which incline towards the north,, and contain 

 shells similar to those in the escarpment of Radkersberg. The hill is sur- 

 mounted by a thin cap of dark-coloured basaltic lava, imperfectly columnar, 

 upon which the village and church stand *, This rock is coarse and granular, 

 with a tendency to concretionary structure, contains olivine, and here and there 

 has the rough, open structure of recent lavas. 



The tertiary strata of Straden strike to the north-west, and are seen in 

 several round-topped eminences, the mineral structure of which may be 

 best understood by the following detailed section of the adjoining hill of 

 Poppendorf. 



4. Section of the Hill of Poppendorf 



If this hill be ascended from the south, it has the appearance of being 

 divided into three terraces. The lower, on which the castle stands, consists 

 of thin-bedded, calcareous sands, marls, and conglomerates ; of blue, grey, and 

 rusty brown colours. They are much concealed by vegetation, but are par- 

 tially bared on the side of a cross road. 



The middle system is, in its general structure^ somewhat like the lower, and 

 is imperfectly exposed on the slope of the hills ; but a water-course enabled 

 us to observe the following succession of strata : 



a. Yellow, micaceous, sandy marlstone. 



b. Blue, green, and yellow marl, separated by bands of ferruginous calc-grit. 



c. Thin layers of indurated sand. 



* The church and principal buildings are made of a beautiful fine-grained oolite, extracted from 

 the adjoining quarries of Freesing and Poppendorf. 



