60 REPORT — 1877. 



The Lower Eed Sandstone lies irregularly and un conformably on the Coal- 

 measures in hollows eroded in its surface, but contains many species of Coal- 

 measure plants. Large quantities of water are pumped from these sandstones, 

 and from the Magnesian Limestone of this. county, for the supply of Sunder- 

 land, South Shields, Jarrow, Seaham, and several villages — the quantity 

 pumped from an area of 50 square miles overlying the Coal-measures being, 

 according to Messrs. Daglish and Forster*, no less than 5,000,000 gallons 

 per day, which abstraction has not in the least altered or lowered the per- 

 manent water-level in the rock of this district, which occurs along the coast 

 at mean-tide level, rising to 180 feet above it inland. 



The following analysis of the Sunderland water is given by the Rivers 

 Pollution Commission : — 



Total solid impurity 4448 



Organic Carbon "035 



Organic Nitrogen '030 



Ammonia 0*0 



Nitrogen as nitrates and nitrites -416 



Nitrogen, total combined -446 



Previous sewage contamination 3*840 



Chlorine 4-17 



{Temporary -8 



Permanent 13*9 



Total 14-7 



The Commissioners comment on the fact that spring water, Waterham's 

 Pield, Pontefract, is not only excessively hard, but differs from the Sunder- 

 land well-water in having a large amount of temporary hardness (24*9) ; but 

 it is important to notice that the water of Sunderland, unlike that of 

 Pontefract, is obtained from the Sandstone beneath the Magnesian Lime- 

 stone, and not from the Dolomite itself. 



These limestones, as stated by the Commissioners, are rarely used as a 

 source of water-supply ; dolomite being a double carbonate of lime and 

 magnesia imparts both these substances to the water. 100,000 lbs. of the 

 Sunderland water contained 5*89 lbs. of lime and 3*96 lbs. of magnesia, 

 which must be due to the percolation of the water through the porous lime- 

 stone before it reached the underlying sandstone. 



These limestones of Durham gradually thin away to the south, through 

 Yorkshire and Derbyshire, and die out near Nottingham. The thin lime- 

 stones of Lancashire, already described, may be considered their debased and 

 argillaceous equivalents, the fossils occurring at Astley and Bedford being 

 the well-known magnesian limestone genera Tragos, Schizodus, BaJcevellia, 

 and Turbo. 



The less crystalline limestones hold 3-45, 6-0, 13-13, 14-87, and even 

 17-0 lbs. of water to the cubic foot. The Sandstones vary less, 10 lbs. of 

 water (a gallon) being the average point of saturation. The more crystallino 

 limestones absorb very little. 



Of these Yorkshire and Nottinghamshire Limestones, the Commissioners 

 give the following analysis : — 



* Report Brit. Assoc. 1863, Newcastle Meeting, p. 726. 



