On the Aerated Barytes. 601 



by an argillaceous cement, fo as to form a very 

 hard aggregate of a reddifli grey colour.* 



The Argillaceous Shiftus, which is called Shiver 

 by the miners, differs little from that which is 

 in general found incumbent upon Coal.f It ap- 

 peared to contain no marine exuvice, but abun- 

 dance of thin laminse of Martial Pyrites between 

 its plates j at leaft this was the cafe with thofe 

 pieces which were found near the vein. 



The Strata dip from Eaft to Weft, with a general 

 declivity of about five inches in two yards. Thofe 

 on the North fide of the veins, or towards the 

 valley, lie fix yards deeper than the correfpond- 

 ins ones on the South. 



* I have no doubt that thefe Strata of Sand-ftone, as well 

 as many others of the fame nature, originate from Gra- 

 nite Mountains, which in fome of the great revolutions 

 of the globe, were in part deftroyed, or wafted by the 

 violence of the waters, forced along with the irrefiftible 

 torrents, and by them conveyed to, and depofited in the 

 beds where we now find them, where they afterwards con- 

 folidated. I am led to this conjefture, not merely from 

 the general method of accounting for the formation of 

 Stratified or Secondary Mountains, but more efpecially from 

 having obferved in thefe Sand-flones all the component 

 parts of Granite, Quarz, Mica and Feltfpar, the lalt of 

 which in general forms the cement, though diftinft cry- 

 llals of it are alfo inteifperfed in the mafs. 



f Vide Forfter's Introdu6tIon to Mineralogy, Shiftus 

 friabilis, p. 14; alfo Berkenhout's Natural Hiftory of 

 Great Britain, part III. p. J4. It is omitted in Kirwan's 

 Mineralogy, as alfo in Magellan's Cronftedt. 



The 



