312 PROCEEDINGS COTTESWOLD CLUB 1912 



the surface of the sand of the required carbonic acid by decom- 

 position of the various organic materials that pertain to the 

 refuse matters of human occupation. These refuse matters 

 also supply much nitrogen, which, by decomposition of the 

 compound organic bodies in which this element occurs, is 

 destined to pass through the form of ammonia to appear ulti- 

 mately in the water as fully oxidised nitrate, and the propor- 

 tionately large quantity of nitrate contained in the water 

 yielded by wells sunk in the sand within the region of streets 

 of houses with their accompanying sewers, drains and great 

 surface pollution is characteristic, and constitutes a rough 

 means of estimating the relative degree of pollution to which 

 the water has been locally subjected. Upon analysis, better 

 results are obtained from water yielded by wells towards the 

 edge or upper part of the sand-bed as a rule, than that yielded 

 by wells in the middle and lower parts of the town where 

 the oxidation of the nitrogen is also frequently found to be 

 less complete. 



Accompanying the excess of nitrate an increase in the 

 amount of chloride is invariable, as well as a large addition to 

 the hardness and the general sohd content of the water. The 

 dissolved mineral matter in the water derived from these wells 

 often includes a considerable proportion of sulphate and some 

 amount of magnesia. These may be chiefly derived from the 

 clay that underlies the sand, by reason of the well being sunk 

 some distance into the clay, or by a saline spring issuing from 

 the surface of the clay in the neighbourhood of the well. 



In passing, it may be mentioned that the wells situated 

 in the sand bed and subjected to the polluting sources above 

 set out, have all been closed within the last twenty years in 

 favour of the general town service, which has been extended 

 to nearly all the houses in Cheltenham formerly supplied by 

 wells. 



Beyond the borders of the beds of sand, wells have often 

 been sunk into the clay ground, though never, as in the case 

 of the sand, with the practical certainty of striking a good 

 store of water, but always on the hazard of obtaining a supply 

 that might be sufficient in quantity and in quality for all 



