1818.] Geological Transactions, Vols. III. and IV. 223 



W.N.W. at a low angle, and the entire thickness of the series 

 has been estimated at 2700 feet and upwards. Some of the 

 members of this formation agree with those of the coal-field, viz. 

 coal, shale, and sandstone ; but other beds also occur which 

 sufficiently distinguish this formation from the preceding. These 

 are sandstone with impressions of marine shells, shale, and 

 limestone, containing fossil encrini, chert, and basalt, in apparent 

 beds, or overlying masses. 



The great mining fields of Aldstone, Dufton, and Arkendale, 

 are situated in this formation, the lead ore being chiefly found 

 in the thicker beds of limestone. The only abundant ore of lead 

 is galena, which here yields about 60 per cent, of metal. The 

 general average of silver which the lead contains is about 12 oz. 

 per ton. About 9000 tons of lead, the produce of this district, 

 are annually shipped from Newcastle and Stockton. 



Calamine is worked in some places, and blende occurs in 

 greater or smaller proportion in all the mines. Copper has been 

 Found in small quantities, but not in sufficient abundance to be 

 worth working. 



3. Description of an insulated Groiip of Rocks of Slate and 

 Greenstone in Cumberland and Westmoreland, on the east Side of 

 Appleby, bettveen Melmerby and Murton. By the Rev. W. 

 Buckland, Professor of Mineralogy in the University of 

 Oxford, 8cc. 



The district here described commences at the south-western 

 extremity of the lead mine measures described in the preceding 

 paper. These measures basset out, forming a series of lofty hills 

 which extend N. and S. and form the great watershed of the 

 country; the streams rising from their eastern slope running 

 into the German Ocean, and those rising from their western slope 

 running into the Irish Channel. The eastern side forms a series 

 of precipitous faces, at the base of which the old red sandstone 

 may be seen supporting the limestone, and resting upon the 

 almost vertical edges of greywacke slate. On the western 

 boundary of the slate is a line of greenstone, sometimes appa- 

 rently vertical and adjacent to the slate, often covering it, and 

 swelling into small hills ; here and there the greenstone either 

 is intersected by veins of a granite, chiefly composed of felspar, 

 or, perhaps, itself passes into this rock. On the west of the 

 greenstone the limestone formation appears to be resumed ; but 

 instead of being nearly horizontal and occupying a large tract, 

 it is seen adjacent to the greenstone, in nearly vertical strata 

 much broken and intermixed with each other, which soon dis- 

 appear below the surface. Along the greatest part of the line 

 the limestone is entirely wanting, and the red marl, exhibiting 

 the usual characters of that rock, and forming nearly horizontal 

 beds, abuts immediately against the greenstone. At the south- 

 ern extremity of the tract here described, near Murton, the 

 greenstone is wanting, and the red marl comes close up to 

 the greywacke, and even in some cases covers the greywacke, 



