Vol. 63.] ATTKIBUTED TO THE SAVOY AND SWISS ALPS. 299 



which the term ' flow ' is less applicable. In the case from the 

 Col de Brion, would the superincumbent weight be sufficient ? 

 We may ask the same question in several other instances, which 

 also demand no small plasticity in the rocks represented. What- 

 ever allowance we may make for subsequent denudation, the 

 thickness of the sedimentary deposits, in the part of the Alps of 

 which Prof. Lugeon treats, can never have been very great. The 

 Trias between the Ehone and the Eeuss is generally thin, and 

 sometimes absent ; the remainder of the Secondaries are fairly 

 represented, but the whole, so far as I can ascertain, probably does 

 not exceed 8000 feet. Even if we add part of the Elysch x with 

 the rest of the Eocene, 12,000 feet of rock would be the maximum 

 available for putting pressure on the rocks below. 2 In our own 

 country, not to speak of others, rocks can be examined which have 

 undergone quite as severe a pressure, and yet have remained 

 unaffected. There are flexures, with thrust-faults, in the Northern 

 Highlands; foldings enough in the Southern Uplands ; beds that have 

 been heavily loaded in the English Pennines, but no migrations of 

 masses such as are claimed for this Alpine region, so that here we 

 must suppose the poet's words to have come true : 



' The hills are shadows, and they flow 



From form to form, and nothing stands.' 



To return, however, to the experiments with cobblers wax. In 

 those recently described, layers, representing, let us say, the Jurassic 

 and the Cretaceous formations, were bent, when forced over a single 

 obstacle, into more or less horizontal lobate folds ; then, after passing 

 a second one, both obstacles being of considerable magnitude, were 

 either doubled into flat folds or torn asunder into isolated bandlets, 

 which might be compared with ' klippen.' But did these experi- 

 ments bear much real resemblance to the processes at work in the 

 making of the Alps ? The layers of cobbler's wax were originally 

 wedge-shaped, and the uppermost (ad), in the second experiment, 

 only just overtopped the higher obstacle and was overtopped by the 

 more distant though lower one. As its outer surface gradually sank, 

 other layers of the material were added, the total thickness of these 

 apparently being about equal to the maximum in the original 

 wedge. Movement was the result of gravitation, which, under 

 simpler conditions, would have changed the wedge into an oblong ; 

 as things were, it squeezed outwards and forced over the obstacles 

 some of the original and of the added material. The cobbler's 

 wax, in short, as was to be expected, behaved as a viscous fluid ; 



1 Very commonly a portion only of the Flysch is included in this travelling 



2 It is true that the Flysch is said to be more than 2000 metres thick in 

 Dauphine (A. de Lapparent, ' Traite de Greologie ' 1883, p. 1012), but as the whole 

 of it could not at once set the underlying beds in motion and make so long a 

 journey to the north, the amount allowed is probably not an underestimate. In 

 regard to the Mysch, I may say (although the matter is too long for discussion) 

 that I find it difficult to accept some of Prof. Lugeon's views concerning the 

 origin of the breccias containing ' exotic ' rocks. 



