34 THE SHALLOW AND DEEP WELL WATERS OF ESSEX. 



since only been used for slopping purposes. What caused this 

 change ? — the deepening of the well, or the process of shelling, which 

 may have destroyed the continuity of the tube and allowed water 

 from some source at a lesser depth to enter ? This is a question 

 upon which I should like to have your opinions. 



My analyses of the deep well waters are divided into three 

 groups. 



1. Those of waters not exceeding 5" of hardness. 



2. „ with a hardness of over 5", but not 



exceeding 10". 



3. „ with a hardness exceeding 10". 



(I may here remark that the depth of the wells given in Col. I. are 

 almost all taken from Mr. Whitaker's Sections, and that it is toler- 

 ably certain that the water from the wells of unknown depth is from 

 the Tertiary sands.) 



In each of the three groups we find waters from both the chalk 

 and sands, and it is impossible to tell from the analyses from which 

 source the water is obtained. Take, for instance, the first group, 

 Table III., the waters from the very carefully made wells of the 

 Southend Waterworks Co. — wells sunk expressly to exclude all water 

 except that coming from the chalk. Compare these with the water 

 from the Tertiary sands at Woodham Ferris, Rettendon, and 

 Runvvell. All contain very small quantities of lime salts, and a 

 considerable amount of chloride and carbonate of sodium. At 

 Brentwood, and south of Brentwood, however, the soft chalk waters 

 contain much less salt {vide^ waters from Brentwood Asylum, Pyrgo 

 Park, and Britannia Works, Ilford). A few of these waters contain 

 a larger quantity of sodium chloride than the others, more espe- 

 cially the chalk water at Tiptree Brewery, and the sand water at 

 Bridgewick Farm, Dengie. The latter is close to the sea, the 

 former many miles distant. The soft waters obtained near Maldon 

 also contain an excess of salt ; but the wells here are close to a tidal 

 basin. If the salt, however, be due to infiltration of sea water, how 

 is it we obtain no indications of the presence of magnesia ? I may 

 also draw your attention to the fact that nearly all these soft waters 

 are exceptionally pure, as indicated by the small quantities of 

 nitrates present. 



When we examine the second group (Table IV.), we find there 

 are only three chalk waters (two at Colchester and one at East 

 Donyland, near Colchester). These differ somewhat in character. 



