A. J. Jukes-Browne — Physiography of the Lower Trias. 221 



Sea has been excavated by the tidal scour is surely a complete 

 assumption ; by many it is regarded as an ancient submerged valley. 



2. If the waters of the Lower Trias were marine, Prof. Bonney 

 naturally asks in which direction they communicated with the open 

 sea? The group thins out both northward and southward, and it is 

 also doubtful whether there was any connection hetween the eastern 

 and western basins at this period. The Bunter beds are thickest in 

 North Cheshire, and if there was any communication with the open 

 sea, Mr. Beade must be prepared to bring in the Atlantic either 

 through St. George's Channel or the North Channel. 



3. The question — Could such thick pebble-beds be accumulated 

 on a sea floor? — is certainly one which requires an answer, and has 

 not been answered by Mr. Beade. 



To sum up, it seems to me that each advocate has one strong point 

 which has not been met by his opponent, and that one or the other 

 of these difficulties must be explained before either theory can be 

 accepted as geological history. 



If the pebbles were brought from Scotland in Triassic times, as 

 Prof. Bonney believes, how did the largest pebbles get spread out 

 into a conglomerate 90 feet thick at that end of the basin which 

 would be farthest from the source of the river? 



If on the other hand we are to entertain the introduction of a 

 Triassic sea, Mr. Beade must not only indicate how its waters gained 

 access to the midland counties, but how such thick beds of pebbles 

 could be accumulated beneath this sea. 



With regard to the nut that Prof. Bonney's hammer is expected 

 to crack, I would like to ask why he feels so sure that the pebbles 

 came from Scotland in Triassic rivers, and why they should not 

 have been derived from some still older conglomerate, the remnants 

 of which are now concealed from view. The existence of a breccia 

 at the base of the Bunter conglomerates in Worcestershire is an 

 interesting fact. Are the contents of the breccia all of local origin, 

 or are there quartzites among them ? 



With respect to the accumulation of pebble-beds. I think Mr. 

 Beade might have asked Prof. Bonney why he need assume that the 

 water was deeper in the south than the north ? Triassic levels were 

 not the present levels, and though Prof. Bonney's theory demands 

 a continuous southerly slope, that of Mr. Beade does not, and I fail 

 to see why there must have been deep water over Central England 

 in order to bring tidal waves over the north-western region. 



Finally, is there any proof that the pebble-beds were laid down 

 everywhere at the same time, and might not the Staffordshire beds 

 have been originally beaches at the head of a bay, subsequently 

 spread out and distributed by storm waves (not tidal waves) during 

 a somewhat rapid subsidence of the area? Could not submarine 

 pebble-beds of considerable thickness be formed in this way ? I am 

 only suggesting an answer to Prof. Bonney's question, and asking 

 for its consideration. I am not adopting it as a theory, for I cannot 

 yet see that there is a single item of positive evidence for the marine 

 origin of the Lower Trias. 



