66 Professor T. Q. Bonney [April 4, 



the Diablerets, or help to form the mountain masses near the Todi, 

 rising in the Bifertenstock to a height of 11,300 feet above the sea. 

 Still there are signs that the sea was shallowing and the epoch of 

 earth movements commencing. The Eocene deposits of Switzerland 

 include terrestrial and fluviatile, as well as marine remains. Beds of 

 conglomerate occur, and even erratics of a granite from an unknown 

 locality, of such a size as to suggest the aid of ice for their transport. 

 For the present I prefer, for sake of simplicity, to speak of the uprais- 

 ing of the Alps as though it were the result of a few acts of compres- 

 sion, though I am by no means sure that this is the case. Thus 

 speaking we find that in Miocene times a great mountain chain existed 

 which covered nearly the same ground as the present Alpine region of 

 mesozoic and crystalline rocks. To the north, and probably to the 

 south, lay shallow seas, between which and the gates of the hills was 

 a level tract traversed by rivers, perhaps in part occupied by lakes. 

 Over this zone, as it slowly subsided — in correspondence, probably, with 

 the uplifting of the mountain land — were deposited the pebble beds of 

 the nagelflue and the sandstones of the molasse. 



Then came another contraction of the earth's crust ; the solid moun- 

 tain core was no doubt compressed, uplifted, and thrust over newer 

 beds, but the region of the softer border land, at any rate on the north, 

 was apparently more affected, and the subalpine district of Switzerland 

 was the result. I may here call your attention to the fact that, whether 

 as a consequence of this or of subsequent movements, the miocene 

 beds occur on the northern flank of the Alps at a much greater height 

 above the sea than on the southern, and have been much more 

 upraised in the central than in the western and eastern Alps. Further, 

 between the Lago Maggiore and the south of Saluzzo mesozoic rocks 

 are almost absent from the southern flank of the Alps, and the miocene 

 beds are but slightly exposed and occupy a comparatively lowland 

 country. I think it therefore probable that the second set of move- 

 ments produced more effect on the German than on the Italian side of 

 the Alps, causing in the latter a relative depression. In support of this 

 view we may remark that the rivers which flow from the Alps towards 

 the north or the west start, as a rule, very far back, so that the water- 

 shed of the Alps is the crest of the third range reckoning from the 

 north, and the great flat basin of the Po is the receptacle for a series 

 of comparatively short mountain rivers. These also take a fairly 

 straight course to the gates of the hills, while the others change not 

 seldom from the lines of outcrop to the lines of dip of the strata — a 

 fact I think not without significance. To this rule the valley of the 

 Adige in the eastern region is an exception. May not this be due to 

 the remarkable series of minor flexures indicated by the strike of the 

 rocks (secondary and earlier) immediately to the west of it, which 

 probably influences the course of the Adda and can, I think, be traced 

 at intervals along the chain as far as Dauphine ? Be this as it may, it 

 is obvious that the generally uniform E.N.E. to W.S.W. strike of tho 

 rocks which compose the Alpine chain is materially modified as wo 



