36 THE SHALLOW AND DEEP WELL WATERS OF ESSEX. 



much sodium chloride and carbonate. On the other hand, in the 

 central portions of the county the waters from the sands and the 

 chalk beneath are practically identical. ( Vide also Whitaker's 

 " Geology of London," vol. i., 514.) How are these differences and 

 agreements to be accounted for ? What is the source of the 

 carbonate of sodium found in both the sand and chalk waters 

 throughout the county ? Possibly the water under the central and 

 eastern portion of the county, whether derived from the Tertiary 

 sands or the chalk, is from one and the same source. 



Near the outcrop of the chalk, the water is undoubtedly derived 

 from that portion of the rainfall which percolates into the chalk or 

 passes in through fissures from the superficial sands. Is the water in 

 the deeper portions, under central and east Essex, in part derived 

 from the sea, the character of the water being altered by the sands or 

 chalk through which it percolates? (The abundance of chlorides 

 and of magnesia salts would seem to indicate a much more direct 

 corinection between the sea and the wells in several localities.) 

 Could slow filtration of the sea water, through such strata as we find 

 beneath the clay, remove certain salts from the sea water and at the 

 same time by some chemical action give rise to the formation of the 

 carbonate of sodium found in these waters ? If so, these saline 

 waters would naturally be found at the lower levels, whilst the 

 water percolating into the chalk near its outcrop, being less dense, 

 would, as it were, float upon it, and the line of demarcation might be 

 defined by the examination of waters from various depths and from 

 various parts towards the south, west, and north of the county. 



The discussion of the relative values of these deep well waters 

 for domestic purposes is beyond the scope of the present paper; but 

 is one to which I am devoting some attention. 



I had not intended publishing my analyses, or a paper on this 

 subject, until many more samples of water had been examined; but I 

 have had so much difficulty in obtaining samples from well authenti- 

 cated sources, and have been so perplexed with the variations found, 

 that I decided to communicate to the Field Club ths results already 

 obtained in order to elicit criticism and opinions, and, if possible, to 

 obtain the aid of its members in conducting further researches, 

 which can scarcely fail to yield results of an interesting character. 



