718 HANGING VALLEYS IN THE ALPS AND HIMALAYas. [ Nov. 1902, 
said about the main and side valleys; he believed their formation 
to be simultaneous, but the main stream would be more energetic, 
because it was augmented by the lateral ones. Mr. Marr was quite 
right as to the importance of study of individual instances, but the 
speaker had examined a very large number, for he had been at 
work on such questions for fully forty years, and in the Alps the 
rock-masses were on a larger scale than in English hill-countries, 
so that explanations of lines of weakness would not so generally 
apply in the former as in the latter. To Mr. Mackinder, he observed 
that the floors of the hanging and the main valley did become 
nearer in going up the latter, but he could not see how a hanging 
valley should occur at its head, for there could not be any dif- 
ferential motion to cause it. To Mr. Lamplugh, he replied that 
inferences from the action of moving masses of ice upon a soft 
material were not of much value when transferred to hard rock ; 
personally, he did not feel gratitude for papers written after hurried 
journeys. Hehad preferred to spend about ten years in examining 
these valleys, for he did not believe that science was benefited by 
hasty generalizations. 
Prot. Garwoop, in reply to Mr. Lamplugh, said that he had tried 
to avoid too much generalization on glacial erosion, as it was a 
large subject, and had confined his views to the four districts 
described in the paper. He quite agreed with him that the surfaces 
of upland districts were liable to have the disintegrated material 
removed by ice, and the solid rock grooved and polished, and he 
pointed out in his paper that this had happened in the Val Ticino 
since the overdeepening of the main valley. He thanked the 
Fellows for their reception of his paper. 
