MELLARD READE : THE NEW RED SANDSTONE. I09 



ot'ners, though I am not aware that it has been noticed before as 

 specially characterising the building-stones. In fact it may be said 

 that the value of the building-stone is in direct relation to this 

 deposition of silica. Some of the sandstones are very soft when 

 quarried, but stand the weather remarkably well, as may be seen in the 

 stone of the Town Hall and many other buildings in Liverpool, and 

 the excellent examples in Shrewsbury of Grinshill stone. Such is the 

 fame of these quarries, that the good people of Shrewsbury seem to 

 think all building-stone comes from Grinshill ! As I have already 

 said, the bulk of the grains are of quartz, but there is also felspar 

 present, and occasionally mica. The stone varies very much in 

 quality, as it does in most sandstone quarries, the defect of the Store- 

 ton stone being the frequent presence of galls of grey marl. The 

 development of the crystals of quartz is doubtless due to the porosity 

 of the stone, which while allowing the circulation of water, also 

 gives interstitial space for the pyramidal growths on the grains. 

 Some of the best of these building-stones, I have proved by 

 experiment, will hold as much as three quarts of water to the cubic 

 foot*; and it is this capacity for absorption that makes the Triassic 

 Sandstones such excellent water-bearing reservoirs. These details, 

 familiar to those who live on the Triassic areas, are interesting in 

 themselves ; but they are doubly so when we try to picture how 

 their characteristics came about. How, indeed, can we account for 

 the enormous development of siliceous sands, to the exclusion of 

 materials of the rocks of the basins in which they lie ; for local frag- 

 ments would seem to be principally confined to the conglomerate beds, 

 such as are to be found in great development at Bridgenorth ? If 

 the quartz grains are derived from the degradation of granite rocks, 

 what has become of the other constituents of the granite ? It is true 

 there are occasional beds of marl intercalated in the sandstones, but 

 it is only in the upper part of the Trias that any great development 

 of marl occurs, and in this are found the salt-beds for which Cheshire 

 is so distinguished. 



The distribution of sediment by water is dependent upon the 

 size of the grains and the velocity of the currents ; hence it would 

 seem that very uniform conditions must have prevailed over a large 

 area for a lengthened space of time during the laying-down of the 

 Triassic Sandstones. It appears to me that these conditions could 

 not very well obtain in a lake, for lakes as a rule are distinguished 

 for the fineness of the sediment laid down in their deeper parts; and 

 one would also expect to find calcareous beds and fine-grained mud- 



* Experiments on the Circulation of Water in Sandstone. — Proc. of Liverpool 

 Geol. Soc, 1883-4. 

 April 18S9. 



