AND ASSOCIATED PERMIAN ROCKS OF DURHAM. 209 



taken as the area of the Lower Red Sandstone in North Durham, 

 would give 69,696,000,000 gallons, or thirty- eight years' supply, 

 at 5,000,000 gallons per day. 



As a building stone, that portion of the deposit from which the 

 samples analysed were taken, is of no use, though the lower 

 micaceous beds are occasionally quarried for that purpose. The 

 presence of oxide of iron prevents it being employed in the 

 manufacture of glass. 



Sub-foemation— M AEL - SLATE . 



Geological Characters. — A yellow and grey, well laminated cal- 

 careous shale or slate — sometimes hard and ringing under the 

 hammer, but generally soft and somewhat tough : fossiliferous. 

 It varies in thickness from two feet to nearly ten feet, and is 

 almost invariably found between the limestone and the Lower 

 Red Sandstone in Durham. 



No. 7. Locality— RYHOPE PIT. 



Lithological Characters. — Dark grey (commonly called blue) 

 softish Marl-slate, containing the scales of Palceonisci. Lowest 

 laminae. 



ANALYSIS. 



Carbonate of lime 16-64 



magnesia 12-56 



Oxide of iron and alumina 3 - 76 



Silica soluble in dilute acid 2*00 



Sand, &c 4512 



Water, &c 19-92 



100-00 

 No. 8. Locality— RYHOPE PIT. 



Lithological Characters. — Grey, hard, and almost sub-crystal- 

 line, laminated Marl-slate, containing a small vein of calcite, 

 with crystals of iron pyrites. Upper laminae. 



