304 Professor Sedgwick and Mr. Murchison on the 



secondary rocks on the outskirts of the chain^ however anomakjus their dip or 

 j)osition, belong in general to the newest part of the series. But when we 

 pass to the west side of the great chasm through which the Inn escapes into 

 the plains at the northern base of the Alps, the dislocations become much more 

 complex; and there are, if we mistake not, two distinct axes of elevation 

 ranging nearly parallel to each other; one through the old central line of the 

 Alps, the other through the centre of the northern calcareous zone. The 

 effect produced by the second axis is such, that some of the higher secondary 

 calcareous groups are carried, with an inverted dip, right against the old 

 rocks of the central chain, and appear to pass under them. This extraordinary 

 derangement of the strata passes through the dolomitic peaks of the Rhetian 

 Alps at Mittenwald ; and we have been informed, that derangements of a 

 similar kind have been traced into the heart of Switzerland. 



Notwithstanding the difficulties arising from these great derangements in 

 tiie relative position of the formations, and the frequent absence of any dis- 

 tinct mineralogical subdivisions, the successive deposits of the great chain 

 may, we think, be separated into a series of natural groups, admitting of at 

 least a general comparison with the principal geological groups of England. 



These natural groups, in the ascending order, are as follows. 1. Primary 

 crystalline rocks forming the mineralogical axis of the chain. 2. Crystalline 

 rocks with calcareous beds, in some rare instances containing traces of 

 organic remains ; the system graduating, at its upper extremity, into rocks 

 conforming to the ordinary transition type. 3. Red marl, sandstone, and 

 niagnesian limestone, &c. &c. ; with subordinate beds and masses of gypsum, 

 and, more rarely, with rock salt. 4. Older Alpine limestone. 5. Shale lime- 

 stone and sandstone, with brecciated saliferous deposits. 6. Younger Alpine 

 limestone — The groups 4, 5, 6, are supposed to represent the lias and oolitic 

 series. 7. Alternations of limestone, calcareous gritstone, sandstone, and marl. 

 Sec. &c., with numerous impressions of fucoid bodies, and sometimes with other 

 fossils, apparently of the age of the green-sand or chalk. 8. All deposits 

 superior to the chalk, comprehending several distinct tertiary groups. 



In the paper above alluded to, the sixth and seventh groups were both 

 included in the "younger Alpine limestone." But we distinctly stated, that 

 under this name were comprehended two groups of deposits; the lower '' com- 

 mencing in theuppersystemof the oolitic series," and the upper "terminating ^j 

 on the outskirts of the chain, in ridges of indurated shale, sandstone, and lime- 

 stone, supposed to be the equivalents of the green-sand and chalk*." We 

 lurther staled, "thai these outer ridges appeared to be greatly expanded 



* See Phil. Mag. and Annals, N.S. vol. viil. August 1830. « 



