320 Professor Sedgwick and Mr. Murchison on the 



precipices of the older limestone* : and although we did not attempt to follow 

 their range^ and had few observations to oiler respecting them which we 

 thought worth recording, we were acquainted, through the maps of Keferstein, 

 with the general facts of their geographical distribution. 



The peculiar character and position of this group when regarded as a whole, 

 the importance given to it by the elaborate descriptions of Dr. Boue, and its 

 enormous expansion in some of the eastern parts of Europe, make it con- 

 venient now to separate it from the older secondary system of the Alps, and 

 to consider it as a distinct formation. Whether it be called Flysch or Vienna 

 grit, or by whatever name it be hereafter designated, is a matter of very small 

 importance. 



It will be our object to show, in the subsequent details of this paper, that 

 some portions of this group admit of at least two subdivisions; a lower, cha- 

 racterized by the Vienna fucoid grits and shales ; and an upper, here and 

 there abounding in Nummulites and many other fossils, and containing sub- 

 ordinate beds of arenaceous iron ore : the two are, however, so intimately 

 blended, and have so many characters in common, that we do not venture to 

 separate them ; but consider them together, in a general way, as the repre- 

 sentatives of the green-sand and chalk. We shall endeavour further to show 

 — that the nummulitic series is enormously developed, and that in some parts of 

 the chain it is placed so exactly on the confines of the secondary and tertiary 

 systems, that the lower portions abound in fossils almost exclusively secondary, 

 while the upper portions contain a great excess of tertiary genera or species 

 — in short, that on the north flanks of the Alps there is an occasional passage 

 from the secondary to the tertiary systems. 



To convey a correct, general notion of the distribution of this formation, we 

 must refer to the small, coloured map accompanying this paperf , which has 

 been constructed partly from our own observations, and partly from the 

 inedited maps of M. Partsch of Vienna, and also from an inedited map of 

 the Archduchy of Austria, transmitted by Dr. Boue to the Geological Society 

 during the past year;];. 



Jt was not our object to trace this system into Switzerland, where it appears 



* The same remark applies to the corresponding series on the south flank of the cliain. Thus 

 the scuglia and green-sand of the Possagno Hills, forming an outer fringe of the Alps of Bassano, 

 are verdant to their summits (2000 feet above the tertiary deposits), and form a striking contrast 

 with the bare, arid faces of the neighbouring mountains. 



t Plate XXXV. 



1 M. Partsch occupies a considerable part of every summer in collecting materials for a geo- 

 logical map of the Austrian Alps, &c. Detached sheets of the Austrian ordnance map arc 

 coloured by him, year by year, on the spot; and when the survey is completed, the colours will 

 be transferred to a general map on a smaller scale, and published. 



