io8 



THE NEW RED SANDSTONE 



AND THE 



PHYSIOGRAPHY OF THE TRIASSIC PERIOD. 



T. MELLARD READE, C.E., F.G.S., F.R.I. B. A., 

 Park Corner, Bliaidellsatids, near Liverpool. 



Perhaps there are few rocks that at first sight appear less interesting 

 than the Triassic Sandstones, yet to the physical geologist the 

 monotonous uniformity of their constitution constitutes their interest. 

 It is certainly tantalising to traverse hundreds of square miles of 

 country and find the only variation in the constitution of the rocks 

 to be in the colour, size, and form of their constituent grains, and 

 the presence or absence of quartzite pebbles. But when we 

 come to reflect upon the cause of this wide-spread similarity, our 

 difficulties, and therefore our intelligent interest begins. The 

 Triassic Sandstones of Lancashire and Cheshire contain extremely 

 few derived fragments of the rocks of the basin in which they lie. 

 A few Carboniferous pebbles and an occasional derived Carboniferous 

 Limestone fossil are all that can be found to reward a careful searcher. 

 The vast bulk of the grains of which all the sandstones are 

 composed are of quartz, and the nature of a particular stone is due 

 to variations in their size and in their comparative angularity or 

 roundness. In some cases, as in the Upper Bunter at Runcorn, the 

 rock may be described as composed of microscopic pebbles, so 

 perfectly rounded are they ; the intense red colouration being due 

 to a coating of ferric oxide. The grains seem to be simply in contact, 

 and there must be very little cementing silica, as the rock crumbles 

 to pieces in the hand, the grains running like small shot. The 

 Upper Bunter of Ness Cliff in Shropshire is in general appearance 

 and brilliancy of colour the same rock, but an examination with the 

 microscope shows that the grains are smaller and angular. This 

 stone is used for building purposes. The Bunter of Bridgenorth in 

 Shropshire is like that of Runcorn. These ' millet seed ' grains, 

 though distinguishing the Upper and Lower Bunter, are not confined 

 to them. When, however, we come to examine the true building- 

 stones of the Trias, such as the Keuper of Storeton in Cheshire and 

 of the great quarries of Grinshill in Shropshire, or the Bunter of 

 Woolton, Everton, Pex Hill, and innumerable other places where 

 building-stone is quarried, we find that the rock glistens and sparkles 

 in the sun. An examination with the microscope shows that this is 

 due to a crystal growth upon the individual grains, presenting true 

 reflecting surfaces. This deposition of secondary quartz has been 

 pointed out by Bonney, Sorby, J. A. Phillips, G. H. Mort on, and 



Naturalist, 



