302 . Scientific Intelligence. 



larly in the Zurich valley and its neighborhood, appear to be 

 well established. As they differ from the usual interpretation of 

 the phenomena, their reproduction here will call the attention of 

 our readers to their importance. 



*^ It will be observed that the conclusions at which I have 

 arrived in this paper differ in some respects widely from the views 

 recently enunciated by several Swiss geologists. More especially 

 does this difference relate to the question whether the principal 

 Subalpine valleys were excavated before or after the first or 

 Upper Pliocene glaciation. 



Apart from the evidence I have adduced, my conclusion that 

 the first glaciation found the principal Subalpine valleys already 

 eroded derives substantial support from the very history of the 

 Tertiary epoch. In Eocene times the Alps had already emerged 

 from the surrounding sea, though as yet only as a group of low 

 islands. The Miocene period witnessed the principal thrusting 

 and folding of the Jura and the Alps : and the products of 

 increased denudation — namely, sand and clay, afterwards hard- 

 ened to Molasse, and fluviatile detritus subsequently cemented to 

 compact conglomerate — were deposited between the two ranges 

 in two freshwater and one intermediate marine series, the latter 

 being formed in an arm of the sea which, towards the end of the 

 Miocene period, still reached from the Mayence basin to the foot 

 of the Alps. The process of folding continuing, the Subalpine 

 Molasse and the enormous banks of conglomerate, too, were 

 raised, notably near the Alps; the sea receded ; the lakes formed 

 in the shallow depressions of the Molasse plateau dried up, and, 

 consequent upon the increased steepness of the Alpine slopes, 

 denudation and erosion set in on a greatly enhanced scale ; rapids 

 and ravines formed ; the great Alpine rivers effected in the Mio- 

 cene Nagelfluh walls those breaches which later on afforded easy 

 and convenient passages to glaciers; and broad valleys were 

 eroded in the soft Molasse strata of the Swiss lowlands, the gen- 

 eral direction of discharge being towards the natural collecting- 

 channel along the foot of the Jura, and thence to the Rhine. 

 Thus, the Lower and Middle Pliocene period in Subalpine Swit- 

 zerland did not witness the deposition of any new rock-forma- 

 tions, but was an unbroken period of erosion and denudation on 

 a prodigious scale. The long duration of this post-Miocene and 

 pre-Glacial period appears the more obvious when we reflect that 

 it was contemporaneous with the formation of the extensive 

 marine beds of the Subapennine hills and of Sicily. 



It is a singular fact that the geological epoch which imme- 

 diately preceded the appearance of man is perhaps the most diffi- 

 cult to unravel. But unless we assume that in this post-Miocene 

 and pre-Glacial period, which Sir Charles Lyell regarded as of 

 incalculable duration, the work of Nature stood still, we are 

 driven to the conclusion that, at the advent of the first Ice-period 

 in Upper Pliocene times, the principal Subalpine valleys were 

 already excavated approximately to their present depth, and that 



