128 OF ORES AND COALS. 



called by the artificers, are made at Hartley, and at Dent's Hole, 

 near Newcajlle. The pyritse are found in flrata, in fmall no- 

 dules ; the marcafites in perpendicular fifTures. They both 

 hold copper, but in fo fmall a proportion that it is not worth 

 working. Sulphur and arfenic is frequently extracted from 

 them. The pyrites is fomc times found folid and unmixed 

 with extraneous matter, both in our lead and coal-works, but 

 chiefly in the former ; of various figures, in irregular clutters ; 

 orbicular, or in large balls ; alfo tabulated, in regular cubes. I 

 have feen large mattes of the firft fort from the lead-mines at 

 Allen-Hands, and of the latter I have a fmall fpecimen from the 

 coal-work at Cbirton, in the form of cubic pfeudo-cryftal ; two 

 cubes joined together, one of them unfortunately mutilated by 

 a fracture, of a pale yellow colour, glaring and mining like po- 

 lifhed fteel. 



Our coal-works are numerous. The principal, for export, are 

 thofe at 



Plefley, Killingworth-moor, 



Hartley, Newbiggen, 



Tyncmouth-moor, Wylam, 



Chirton, Byker, 



Long Benton, Walker. 



Thefe mines are of various depths. The deepeft and of the 

 greateft curiolity is that at 



Walker, by the river Tyne. It is 100 fathom. The feam of coal 

 is 8 feet, and 5 inches and a half, thick. There are two ventila- 

 tors worked with a machine by the help of the fire-engine. This 

 machine is alfo applied to turn a wheel for raifing coals, bring- 

 ing 



