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this I am compelled so far to retrace my own steps as to bring 

 to your recollection the geological subdivisions of the Alpine chain 

 adopted in our published Memoir. We stated that the Eastern Alps, 

 considered in theirgreatestsimplicity,mightbedescribed as amountain 

 chain with an axis of primary rocks, flanked and surmounted by two 

 great secondary calcareous zones, which are in their turn surmounted 

 by vast tertiary deposits, descending on one side into the plains of 

 Italy, and on the other into the plains of the upper Danube ; and that 

 the same great physical region, when considered in more detail, might 

 be separated into formations admitting of a general comparison with 

 those of our own country in the following order, commencing with 

 the lowest. 1. Primary rocks of the central axis. 2. Highly crystal- 

 line deposits graduating in the ascending order into rocks conforming 

 to the ordinary transition type, and containing, though very rarely, 

 transition fossils. 3. Red and variegated sandstone and gypseous 

 marls, sometimes alternating with masses of magnesian limestone. 

 4. Older Alpine limestone — a formation of enormous thickness, sup- 

 posed to represent a part of the oolitic series, and based upon fetid 

 dark-coloured limestone and other strata which we endeavoured to 

 identify with the lias. 5. Limestone and sandstone with great masses 

 of saliferous marls rolled up and encased among the contorted strata. 

 6. Younger Alpine limestone, including all the secondary deposits of 

 the Alps superior to the saliferous system, and containing two distinct 

 groups ; the first of which was supposed to represent the highest 

 portion of our oolitic series, and the second (or Vienna sandstone) the 

 whole system of the green-sand and chalk. 7. Tertiary deposits. 



Between the two subordinate groups of No. 6. we were not able to 

 draw any precise line of separation ; and, to our surprise, we were 

 still less able to define the limits of the secondary and tertiary series. 

 For, sometimes resting unconformably among the serrated peaks of 

 the higher mountains, and sometimes in a position intermediate be- 

 tween the outer zorie of the chain and the tertiary plains descending 

 towards the Danube, we found great complex deposits, apparently 

 graduating at one extremity into the secondary, and at the other 

 into the tertiary system, and abounding in fossils, which in a great 

 majority of the species seemed to conform to the tertiary type. 

 Upon this mixed evidence we concluded that these singular deposits 

 formed a true connecting link between the secondary and tertiary 

 systems of the region; and, though unknown in our own country and 

 the North of France, were to be placed somewhere between the cal- 

 caire grossier and the chalk. 



To the clearing up of this point (on which alone we had any essen- 

 tial disagreement with Dr. Bou6) , Mr. Murchison has devoted the 

 most elaborate details of his recent Memoir. He first describes the 

 extension of the primary axis into the Leitha-gebirge, which thus 

 seems to form a connecting link between the Alpine and Hungarian 

 chains, and notices some new and interesting localities of the mag- 

 nesian limestone and red marl series. He then traces the reappear- 

 ance of the gypseous and saliferous marls, apparently of the age of 

 the new red sandstone, in some longitudinal valleys of the Salzburg 

 Alps ; and by means of detailed sections, fixes the great salt deposits 



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