14 



J. A. PHILLIPS ON THE CONSTITUTION AND 



that two distinct cavities have been produced in its substance. A 

 crystal of iron pyrites attached to a rounded grain of quartz is seen 

 in fig. 7, which, as well as the preceding figure, is represented as 

 magnified to the same extent as the other illustrations contained in 

 the Plate. 



Prolonged digestion in hydrochloric acid removes the oxide of 

 iron, leaving the surfaces of the rounded quartz granules clean 

 and colourless. The minute crystals of quartz which have been 

 formed upon them, however, adhere firmly to the rounded grains, 

 after this treatment, and no stain of ferruginous matter can be 

 observed between their point of attachment and the grain of sand 

 on which they have been formed. It would therefore appear 

 that, although the sand had been covered generally by ferric hy- 

 drates previous to the growth of quartz crystals, these have never- 

 theless originated at those points only where a chemically clean 

 surface of the quartzose nucleus was exposed. An analysis of this 

 sandstone is given, p. 21. 



Sandstones chiefly composed of rounded weather-worn grains occur 

 in the Lower Mottled series, at a depth of 80 feet from the surface 

 at Stock's Well, belonging to the Widnes water-works, and at 

 Scott's bore-hole near St. Helens, as well as at a depth of 260 feet 

 in the Winwiek boring of the Warrington water-works. 



Beds of loose, rounded sand of the age of the Lower Mottled 

 Sandstone are known to occur at Chapel Bridge, Prescot, and in a 

 boring a little east of Newton Bridge, near Warrington. 



Sandstones of this character are met with north of Eccleston hill, 

 and a similar bed belonging to the Upper Mottled group comes to the 

 surface in the yard of the Bridgewater Foundry at Runcorn. By 

 no means, however, do all the sandstones of Lancashire and Cheshire 

 which belong to this geological age exhibit characteristics suggestive 

 of their formation from seolian sands. At Wirral, in Cheshire, as 

 well as sometimes in the neighbourhood of Liverpool, the Pebble- 

 beds of the Bunter are represented by a brownish-yellow sandstone 

 containing numerous pebbles, which is much employed for building- 

 purposes. 



In many of these beds the quartz is almost entirely in the form of 

 minute crystals, or crystalline aggregations, often united by a ferru- 

 ginous cement, which has manifestly been introduced subsequently 

 to the covering of the original grains with crystalline quartz. 

 An excellent example of a non-ferruginous crystallized sandstone 

 belonging to the Upper Mottled group occurs at Town Green, near 

 Ormskirk. This rock is mainly composed of crystals of transparent 

 quartz, of which the edges and angles are beautifully perfect. It 

 is of a far too friable nature to allow of the preparation of thin 

 sections ; but it appears to have little or no cementing material, and 

 to be, to a large extent, merely felted together by the intergrowth 

 of its constituent crystals. It will be needless to remark that the 

 grains of sandstones of Bunter age are not always either rounded or 

 enveloped in crystals of quartz. 



Among the Keupcr division of the Trias sic sandstones, which are 



