296 



PROF. T. G. BONNET ON THE SOUTHERN ORIGIN [Aug. 1907, 



II li II i! 



-<PQQP. 



principles rather than details, for 

 I doubt whether, under any con- 

 ditions which have existed in 

 post-Archaean times, large masses 

 of rock could be compelled to 

 adopt the behaviour which his 

 hypothesis demands. Thus I 

 shall not attempt to discuss his 

 paper in detail (which, even if I 

 possessed the requisite local know- 

 ledge, would be a very lengthy 

 task), but shall deal with its 

 general and axiomatic principles. 

 I must, however, demur to the 

 interpretation of two sections, 

 among those cited in support of 

 his hypothesis, which are taken 

 from a region more familiar to 

 me than the Chablais Alps. The 

 one, starting north of the Ofen- 

 horn, runs through it across the 

 Lepontine Alps to the Yal d' Anti- 

 gorio (fig. 1): the other — gene- 

 rally similar to it — practically 

 follows the line of the Simplon 

 Tunnel. Both exhibit a series of 

 rocks, strongly and progressively 

 overfolded towards the north, 

 which consists of at least two 

 varieties of gneiss, of a mass of 

 ' schiste,' and a limestone, stated 

 to be Trias. The last-named de- 

 posit is a thoroughly crystalline 

 limestone, often dolomitic, and 

 usually associated with dark 

 schists, 1 in which it is generally 

 either low down or at the base, 

 as represented by Prof. Lugeon. 2 

 Its resemblance to any Alpine 

 limestone, certainly of Triassic 

 age, is only chemical. Though 



1 I have always followed J. B. Jukes 

 in restricting this term to foliated 

 rocks. 



2 I follow him in referring the 

 marbles north and south of the water- 

 shed to the same group, though sus- 

 pecting that, in the neighbourhood of 

 the Rhone, he has included (wrongly) 

 in. the Simplon section one or two 

 isolated patches of rauchwacke\ 



