306 SOUTHERN ORIGIN OF THE SAVOY AND SWISS ALPS. [Aug. I907, 



by Dr. Otto Ampferer, which is printed in the Jahrbuch der k.k. 

 Geologischen Reichsanstalt, vol. lvi (1906) p. 543, published on 

 December 15th, 1906. This I had not seen when writing my paper, 

 which was sent to the Geological Society some time before that 

 part of the Jahrbuch reached our Library. If, then, we use similar 

 arguments, the coincidence is fortuitous ; but, so far as I have 

 gathered from a brief glance (which is all that the time at my 

 disposal lately has permitted), we have proceeded in the main along 

 different lines.— T. G. B., June 21st, 1907.] 



Discussion. 



The President, in expressing the regret of the Society that 

 Prof. Sollas should have been prevented by illness from being 

 present that evening, remarked that, in his absence, the interesting 

 paper to which they had listened could not receive the adequate 

 appreciation and criticism to which anything coming from Prof. 

 Bonney was justly entitled. He had not himself a sufficiently- 

 detailed knowledge of the ground referred to in this paper, to 

 entitle him to intervene with any well-grounded opinion regarding 

 the matters in dispute. With respect to the theoretical possibility 

 of the horizontal displacement of vast masses of rock over long dis- 

 tances, it seemed to him that it was largely a question of degree. 

 It had been demonstrated that in the North of Scotland, during the 

 great post-Cambrian movements, large bodies of the lowest and most 

 ancient rocks were driven westwards for a distance of at least 

 10 miles ; and, if this could happen in the comparatively-narrow 

 tract of movement in this country, he thought it conceivable that 

 displacement of a similar kind, but on a much greater scale, might 

 have taken place in the more voluminous chain of the Alps. Then, 

 with regard to the question of the Schistes lustres, he need not 

 remind the Pellows that there had been a long-standing difference 

 of opinion between the Author and those Swiss geologists who had 

 not been able to trace the marked line of division which Prof. Bonney 

 claimed to exist, between what he regarded as a series of ancient 

 crystalline schists and the metamorphosed members of the sedimen- 

 tary formations of the Alps. Into this controversy the speaker did 

 not propose to enter ; but he thought it important that one view 

 of this interesting and difficult Alpine problem should be re-stated 

 so clearly and fairly as it had been in the present paper. 



The Author, in replying to the President's remarks, expressed 

 his regret that a temporary illness detained Prof. Sollas in Oxford, 

 and said that he thought the amount of displacement became 

 important in questions of thrust-faulting, when one portion of the 

 solid crust of a sphere was supposed to slide almost horizontally 

 over another; and, in the case of the Alps, there was no valid 

 evidence of displacement having occurred to such a distance as was 

 required, either in the crystalline foundation or in the overlying 

 sedimentaries. He was well aware that some Swiss geologists 



