MELLARD READE : THE NEW RED SANDSTONE. Ill 



development of the siliceous cement which holds the grains together, 

 and it might, considering the well-known porosity of the sandstone, 

 have been introduced after the formation of the lake. 



Much more remains to be done before the physiography of the 

 Triassic period can be graphically reproduced. Those who are 

 interested in the question will find a very good resume of the various 

 views held by eminent geologists on the subject — which, however, 

 can so far be looked upon only as very sketchy suggestions — in 

 Mr. Jukes Brown's ' Building of the British Isles.' 



I am not aware that tidal action has been invoked by any 

 geologist, before this was written, to account for the current-bedding 

 of the Bunter Sandstones. Wind and fluviatile action have been 

 suggested, and possibly the current-bedding in parts of theTrias may 

 be due to these causes. When, however, we consider the extra- 

 ordinary thickness, especially about Liverpool, of the Bunter Sand- 

 stones, as proved in very numerous well-borings of which I have 

 many records, the presence of large pebbles, and the absence of all 

 indications of shore-lines or land-surfaces, it is difficult not to 

 believe that most of the sand has been accumulated in areas where it 

 has constantly been covered with water. If this be so, there is no 

 agent I know of capable of creating currents at the required depths 

 other than tidal action. That the tides act at enormous depths 

 I have elsewhere shown*; while at the same time the area of water 

 simultaneously affected is great. On the other hand, river action is 

 shallow and local, and the channels would have to change their 

 courses frequently, and cover an enormous area of a shape uncommon 

 in fluviatile deposits, to lay down sedimentary masses like the Bunter 

 Sandstone. 



Of such a phenomenon we find no indications in the rocks 

 themselves. A tidal sea, fed with sand by rivers from a granitic and 

 quartzite area and bordered by sand-dunes and large tracts of sand- 

 covered country, encroached upon by the waters from time to time, 

 seems to me, so far as my present knowledge extends, the most 

 feasible sort of physical conditions for producing such beds as we 

 find put together in the Bunter. These ideas are, however, put 

 forward simply as suggestions to be considered together with those of 

 other geologists already published and discussed. We need much 

 more information than is at present available before the question can 

 be thoroughly thrashed out. In the meantime I thought it might be 

 of some interest to indicate these provisional views. 



* See ' Tidal Action as a Geological Cause' — Proc. of Liverpool Geol. Soc. , 

 1873-4; and 'Tidal Action as an Agent of Geological Change' — Phil. Mag., 

 May 1888. 

 April 1889. 



