Reports and Proceedings — Geological Society of London. 383 



be seriously incorrect) that the altitude of the Alps during the 

 greater part of their existence has remained, unchanged. A rise of 

 temperature of from 6° to 7° Fahr. would have tlie same effect as 

 lowering the district by 2,000 feet ; a rise of 10° would correspond 

 with 3,000 feet. In the latter case the Pennine chain about the 

 headwaters of the Visp would be comparable with the range from 

 Monte Leone to the Ofenhorn. With a rise of 14° glaciers would 

 almost vanish from the Alps, for the snow-line would then be at 

 12,000 feet above sea-level. Thus glacial action in the Oligocene and 

 Miocene ages would be a negligible quantity, and it would gradually 

 become sensible during the Pliocene ; but glaciers would not invade 

 valleys now free from them until the temperature was some degrees 

 lower than it is at pi-esent — in other words, can have only occupied 

 these during a small portion of their existence. 



The author passes in review a number of other Alpine valleys, 

 which lead to the same conclusion. He calls attention once more 

 to the connection of cirques with valleys, to the impossibility of 

 referring the former to glacial action, and to the unity exhibited by 

 all parts of the Alpine valleys, touching upon some structural 

 difficulties which Professor Davis has been content to meet with 

 hypotheses. Alpine valleys in all parts, as the author shows, indi- 

 cate by their forms meteoric agencies other than glaciers, which can 

 only have acted for a comparatively short time and have produced 

 little more than superficial effects. 



3. " The Origin of some ' Hanging Valleys ' in the Alps and 

 Himalaya." By Prof. Edmund Johnstone Garwood, M.A., F.G.S. 



Lateral valleys which enter the main valley marked by discordant 

 grades in the Jongri district of the Sikhim Himalaya have been 

 attributed by the author to Pleistocene elevation and super-erosion 

 of the main valley by water. Similar valleys in the Val Ticino 

 have recently been attributed to overdeepening of the main valley 

 by ice. The author shows that there is no real proof of this ; in fact, 

 the evidence seems strongly to point to fluviatile and not glacial 

 erosion of the main valley. This is shown by the overlapping 

 profiles and river-gorges situated both above and below some of 

 these ' hanging valleys,' and by the fact that a greater relative 

 amount of erosion has taken place towards the upper end of the 

 main valley than at the lower, where the mouths of the ' hanging 

 valleys ' are less elevated. The overdeepening of the main valley 

 is attributed to an epeirogenic uplift in Pleistocene times, consequent 

 on the melting away of the ice-cap, the lateral valleys being merely 

 tilted sideways. This effect is intensified by the protection accorded 

 to the high lateral valleys by ice, which even nowadays still lingers 

 there. Examples from the Maloja district of the Engadine are cited 

 as confirmatory of this. The best preserved of these 'hanging 

 valleys ' in three districts examined by the author all face north- 

 eastward, and show pi-otection by ice ; others not so protected have 

 begun to cut back their gorges to an accordant grade with the 

 main valley. Examples of other types of ' hanging valleys ' not 

 due to the overdeepening of the main valley are given, and proofs 

 of the greater power of water to excavate over ice are assigned. 



