ON THE CIRCULATION OF UNDERGROUND WATERS. 



Gl 



Pontefract, 

 Yorksliire. 



Mansfield, 

 Well, 75 feet 

 deep, Water- 

 works. 



Mansfield, 



Mr. Peat's 



Well. 



Total solid impurity 



Organic carbon 



Organic nitrogen 



Ammonia 



Nitrogen as nitrates and nitrites 



Total combined nitrogen 



Previous sewerage contamination 



Chlorine 



(■Temporary 



Hardness < Permanent , 



Total 



84-92 

 •054 

 •021 

 

 2-673 

 2694 

 26,410 

 5-55 

 26-5 

 408 

 673 



25-24 

 •053 

 •014 

 



•599 

 •613 

 5,670 

 1-40 

 60 

 16-4 

 22-4 



54-32 

 •139 

 •039 

 

 1-888 

 1-227 

 11,560 

 3-20 

 23-4 

 260 

 494 



From Somerset and Devon your Committee has received no returns ; but 

 they would wish to call attention to the classification of the Triassic rocks of 

 the South-Devon coast, recently published by Mr. Ussher* of the Geological 

 Survey, in which he gives the following sequence : — 



1. Upper Marls 1350 feet. 



2. Upper Sandstone 530 „ 



3. Conglomerates 100 ,, 



4. Lower Marls 600 „ 



5. Lower Sandstone and Breccias. . . . 1000 „ 



3580 



But he states that this maximum total thickness is probably 1000 feet 

 greater than the actual vertical distance, but from various causes an estimate 

 is very difficult. 



In Leicestershire, Mr. Plant reports that for many years water good in 

 quality and abundant in quantity has been known to exist at the base of the 

 great gypsum bed which lies in the Upper Keuper Marls. This supply has 

 been proved wherever the marls have been penetrated in wells from 30 to 

 80 feet in depth, and in excavations for brick-making &c. 



In one of these excavations near the town of Leicester, on the base of tho 

 gypsum being reached at a depth of 40 feet and the last layer cut through, 

 a copious supply of clear water burst through in such abundance as to 

 require special arrangements to carry it to an adjacent brook. The water 

 was found to have worn a deep channel in the red marl lying immediately 

 beneath the gypsum. The stream remains constant in dry and wet weather. 



The marls above and below this gypsum bed are quite dry and free from 

 water, and the water occurring in it must be derived from the various out- 

 crops of this bed in Nottinghamshire, Derbyshire, and Leicestershire. 



Mr. Plant has been led to conclude that this water, running constantly at 

 the base of the gypsum bed, must be the source of supply of sulphate of lime 

 found in the underground waters of the Midland Counties ; and he has always 

 found it difficult to account for the water obtained in deep wells (pump and 

 draw wells) in tho Upper Bed Marls of this county whenever the gypsum 

 bed was penetrated; he is now of opinion that, as far as domestic and 

 farming requirements are concerned, in the Upper Bed Marl district, this 

 horizon affords the most abundant and valuable source of supply. 

 * Quart. Journ. Geol, Soe. vol, xxxii. p. "92. 



