lg Mr. N. J. WlNcB on the Geology of 



abundantly impregnated with yellow ochre, which is sold under 

 the name of dies and. 



Fire-stone resembles the grindstone in colour and fracture, but is 

 soft when first worked. The best is quarried at Burradon near 

 Killingworth : glass-house furnaces are constructed with it. 



White post is a fine-grained sandstone, tolerably hard. 



White post with whin consists of alternate laminae of soft and 

 hard sandstone. 



Grey post is a fine grained sandstone, containing a large admixture 

 of clay and sometimes of mica. 



Brown post is a slaty micaceous sandstone. 



Brown post with Coal pipes is a laminated sandstone traversed by 

 strings of black shale and coal. 



Brown post with skamy partings is a light brown sandstone with 

 dark brown laminae. 



Grey whin or Brown whin is a very hard dirty-brown quartzose 

 sandstone, sometimes specked with minute white dots, and at other 

 times containing very small scales of mica : it strongly resembles 

 granular quartz. A bed of this rock may be seen contiguous to 

 the basaltic dyke in Walbottle Dean. 



What is called by the miners Band in coal is commonly com- 

 posed of bituminous shale, clay and iron pyrites ; sometimes of 

 sandstone. Girdle means a thin plate : thus Post girdles are layers 

 of sandstone ; Whin girdles in post are layers of hard quartzose 

 sandstone in softer sandstone ; and Whin girdles in shale are thin 

 beds of argillaceous iron ore in shale. 



The minerals that accompany the coal measures are, 

 Clay ironstone, forming either thin beds or nodules (catheads) 

 in the shale. 



