102 Prof. Sedgwick and Mr. Murchison on the 



general structure of the whole region, but also by numberless 

 internal traverses through every part of the saliferous mass. It 

 is therefore obvious, that the salt of Hallein is subordinate to 

 strata separated from the lower red sandstone and gypseous 

 marls, above described (p. 92), by many thousand feet of the 

 older Alpine limestone*. 



3. Saliferous mass at Ischel. — The salt deposits of Halstadt, 

 Ischel and Aussee are, we believe, very nearly on one geolo- 

 gical parallel; and in their structure and relations to the,- near- 

 est portions of the chain, they seem to be almost identical. 

 The accompanying plan of the Ischel works f, which we owe 

 to the kindness of M. Dicklberger the Ober Bergmeister, will 

 convey a correct notion of the position of the salt mass among 

 the beds of limestone. The neighbouring hills to which the 

 salt is subordinate, in consequence of a great flexure, dip to 

 the south-west. The beds under the salt are argillaceous, 

 and contain some bands of dark-coloured limestone with casts 

 of Ammonites and some bivalves. Over these beds, and im- 

 mediately under the salt mass, are some thin, compact, cherty 

 beds of limestone. The salt mass is a confused, irregular com- 

 pound of gypseous and saliferous marls, &c. ; which has been 

 worked, at the lowest level, through a breadth of about 500 

 Vienna feet, and through a depth, between the highest and 

 lowest levels, of about 1500 feet. These different levels are 

 approached by means of 12 horizontal galleries cut through 

 the inferior beds, as represented in the plan. It deserves re- 

 mark, that here, as at Hallein, the saliferous mass (E) is sepa- 

 rated from the surrounding limestone by bands of dark- 

 coloured gypseous marls (D) not saliferous. The superior beds 

 of limestone (F) are hardly to be distinguished, either by their 

 structure or their fossils, from those which underlie the salt. 



These details are sufficient to explain the nature and posi- 

 tion of the great saliferous deposits of the eastern Alps, which 

 evidently occupy an intermediate position between the older 

 and younger portions of the calcareous zones ; and may there- 

 fore, along with the accompanying strata, be conveniently re- 

 garded as one of the natural subdivisions of the Alpine lime- 

 stone, in which so many of the distinctive characters of secon- 

 dary formations are almost entirely wanting. 



* The relations of the saliferous beds of Berchtolsgaden are not so obvious ; 

 but we have little doubt that they are nearly in the same geological position : 

 for the system is continued northwards across the valley, and passes finally 

 under the ridge which is a prolongation of Untersberg. On this account we 

 think that the saliferous beds of Berchtolsgaden cannot, by any complex 

 series of faults, be brought into comparison with the marls inferior to the 

 older Alpine limestone. 



t Plate II. Fig. 6. 



If 



