Ixviii PHOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



The inland sea which at the commencement of the elevation of 

 the Alps occupied the space between the northern flank of the chain 

 and the Jura, and covered a much greater breadth between Salzburg 

 and Eatisbon, was contracted to so narrow a strait near Chambery, 

 and again on the south of Linz, in Upper Austria, as to render it a 

 very probable hypothesis that a comparatively moderate oscillation 

 or change of levels would close as it were the sluices, and alter the 

 conditions of the basin from a marine inlet to a great lake — from a 

 smaller Baltic to a Lake Superior. The beds of the Flysch, charged 

 in places with fucoid remains, and alternating with the clearly 

 Eocene nummulitic bands, are characteristic of the shore of this 

 ancient arm of the sea, whilst the strata deposited in brackish water, 

 described by.Heer under the term of the Aquitanian etage^, siipply 

 a satisfactory testimony of the slow secular change under which the 

 marine conditions disappeared ; and a vast brackish lagoon formed 

 the intermediate stage. The freshwater deposits which followed, 

 at a period when, as M. Heer agrees, the level of the lake was at 

 no great height above the sea, would belong to a district with a 

 mean temperature (at sea-level) of 10°'52 E. (55°-5 E.), like that of 

 Milan, whilst the winter will have been that of Catania, and the 

 summer that of South Germany. A downward movement ensued, 

 which reopened the communication with the Mediterranean ; and 

 the vast lapse of time which was occupied in the changes of level 

 seems to be expressed by the fact that the marine organisms again 

 migrated, and spread themselves with the abundance of a full de- 

 velopment over the entire region. 



The renewed blockade of the straits was followed by the destruc- 

 tion of all sea-life, by a further deposit of freshwater strata (the 

 upper Molasse), and, according to the theory under review, by the last 

 great elevation of the Alps, which, lifting the entire region, as the 

 west coast of South America has been raised bodily in recent times, 

 transferred the lake and its borders by slow degrees from an almost 

 subtropical climate to one of more temperate character (as witnessed 

 by the lignite or slaty coal of Utznach, Diirnten, (fee), then to a colder 

 one, and ultimately to one of boreal rigour. 



If we consider the lakes of Switzerland to be the reUcs of this 

 former inland sea, their basins divided from one another and modi- 

 fied in form by the unequal action of the physical forces to which 

 they have been subjected, and that their mean height above the sea 

 is 1325 feet, we shall have, by the addition of 3561 feet, or the 

 amount by which it has been already calculated that the north side of 

 the Alps had been uplifted, a total height of 4886 feet as the eleva- 

 tion of its waters above the sea-level. 



The climate of the great Alpine lake and its banks may be readily 

 calculated: the mean annual temperature would be 2° E., or 36-5° P., 

 the mean temperature of the hottest month 51°-8 F., and the coldest 

 21° F.; and whilst this would show a close resemblance to the cli- 

 mate of the northern part of Norway, the proximity of large bodies 

 of water would doubtless cause a greater atmospheric precipitation 

 * Heer, Urwelt der Schweitz, pp. 275 and 282. 



