Prof. T. G. Bonney — Physiography of the L. Trias. 53 



unworthy of being compared with it. The nagelflue and molasse of 

 Switzerland for a greater thickness than even the Trias of Bootle 

 consist only of pebbles and sand. As I have more than once pointed 

 out, the close resemblance of these deposits to the Lower Trias of the 

 northern half of England indicates a similarity of origin ; and though 

 some marine deposits do occur in the Swiss Miocenes, I believe that 

 the freshwater origin of the beds to which I refer is universally 

 admitted. 



(4). The disappearance of the northerly "plateau or Alpine range 

 from which the materials of the Trias have been supplied. Why 

 should it have been destroyed, when a lesser orographic feature 

 like the Pennine Chain remains?" Mr. Mellard Reade does not 

 appear to me to be quite consistent throughout his paper in regard 

 to this objection ; but letting that pass, I reply that the same kind 

 of objection might be brought forward in regard to the Alps and 

 the Jura. The former have lost by denudation much more than the 

 latter. In fact, for very obvious reasons, of two mountain massifs 

 in adjacent regions, the larger is likely to suffer more than the 

 smaller. Further, in asking the question quoted above, Mr. Mellard 

 Reade appears to have overlooked Scotland. 



Having thus noticed Mr. Mellard Reade's chief objections to the 

 fluviatile hypothesis, I will briefly mention one or two which occur 

 to me against the marine alternative propounded by him. 



(1) Even if we regard it as proved that " the tidal wave produces 

 currents acting through the full depth of the water from the surface 

 to the bottom," is there any evidence that these currents would be 

 capable of sweeping about pebbles 3 or 4 inches in diameter — 

 especially in Central England, where, in order to bring the tidal 

 waves over the north-western region, the estuary should be pretty 

 deep? Indeed, in Staffordshire (where I am writing), where 

 evidence of deposit by powerful currents is very strong, pebbles of 

 over 4 inches diameter are rather common. The Bunter here, mutatis 

 mutandis, is identical with the drift bordering the Alps and with the 

 Swiss nagelflue. 



(2) Where, we may ask, can we place the communication between 

 the Triassic estuary of North-west England and the open ocean? 

 I venture to think that this serious difficulty has not been met by 

 Mr. Mellard Reade, and that it cannot be brought with equal force 

 against the advocates of a fluviatile origin for the English Bunter. 

 A river can escape from open country through a narrow passage, but 

 for a great tidal wave, competent to sweep to and fro, as he requires 

 it to do, the gate must be wide and the way broad indeed. 



(3) Have we any evidence to justify us in ascribing thick beds 

 of conglomerate to marine action ? Excepting cases where torrents 

 discharge their contents into rapidly deepening seas — i.e. submarine 

 deltas — can any instances be found of marine conglomerates com- 

 parable with such a deposit as the Bunter, which at any rate in 

 some parts of England (as here) is a practically unbroken pebble bed 

 at least thirty yards thick ? ' I have never myself read of or met with 



1 Generally, as stated by Prof. Hull (Memoir Triassic and Permian Eocks, 

 p. 108, etc.), and, 1 fully believe, much more. 



