78 Mr. N. J. Winch on the Geology of 



the strata of sandstone called bazles are the most productive of ore ; 

 but the lead-bearing veins appear compressed between these hard 

 sills. In Arkendale the sills of chert yield considerable quantities 

 of galena, but this rock does not occur in the mining field further 

 north. In Shale the veins are comparatively barren, and in travers- 

 ing these soft strata weak veins hade considerably. 



The hade of the veins is variable in degree, and in direction. 

 When the veins in Weardale point east and west, they hade towards 

 the south ; but in Allendale and in the Aldstone moor country they 

 generally hade towards the north : the strata are universally elevated 

 on the side towards which the veins dip. 



Veins, that are otherwise favourably circumstanced for producing 

 ore, are more particularly so if the throw or alteration in the level 

 of the beds of limestone, occasioned by the vein, does not exceed 1 

 or 2 fathoms; for then both cheeks of the vein correspond in their 

 nature, and limestone does not become opposed to shale or other 

 barren stratum. 



The following are some of the most remarkable veins in the 

 mining district. 



At Burtree-ford, where an alpine brook first assumes the name 

 of the river Wear, a very strong vein, called the Burtree-ford dyke, 

 crosses the mining field from north to south, and passing on the 

 west side of Allenheads cuts off or at least terminates all the valu- 

 able veins discovered in that mine. This must not be confounded 

 with the basaltic dyke which passes the river at Buriree a little 

 above the cross-vein. In some situations this fissure appears to 

 elevate the strata above 80 fathoms on the eastern side, and in others 

 greatly to depress them, as may be observed at the quarries in the 

 great limestone not far from Allenheads. Contiguous to the dyke 

 the sills rise at an angle of 45°. Practical miners have remarked 



