3© THE SHALLOW AND DEEP WELL WATERS OF ESSEX. 



or less seriously affected by the filthy deposits of the centuries 

 during which Writtle village has existed. In all the gravel waters I 

 have examined I have found that when the chlorine exceeds about 

 two grains per gallon (corresponding to yT, grains of chloride of 

 sodium, common salt), there are other signs of pollution and of 

 change in character due to such pollution. For instance, you will 

 find that whenever the chlorine is high the nitric nitrogen (which 

 is a measure of the amount of nitrates present derived from the 

 oxidation of organic filth) is also high ; whereas generally, but not 

 invariably, when the chlorine is low the nitrogen is low also. 



On Table I. some analyses are given of waters from the Bagshot 

 sands and pebble beds. One peculiarity of such waters is the low 

 temporary hardness (due to carbonate of lime) and the comparatively 

 low total hardness (due to carbonate and sulphate of lime). My 

 attention has been particularly drawn to these waters, because I find 

 they have a powerful action upon lead pipe, and upon iron pipes, 

 whether galvanised or not. I found, however, that I was not the 

 first person to note this peculiarity, since, upon communicating the 

 fact to Dr. Barry, one of the inspectors of the Local Government 

 Board, who is at the present time engaged upoa an exhaustive 

 examination as to the cause of the lead-dissolving power of certain 

 waters, he informed me that Dr. Harcourt had already sent him a 

 series of analyses of waters from the Bagshot beds, all of which 

 waters acted powerfully on lead. Dr. Barry, at the time, appeared 

 to think that this was a property possessed only by waters from this 

 particular source. Analyses showed that such waters contained little 

 or no carbonate of lime (temporary hardness) and therefore had no 

 alkaline reaction ; and in the north of England, where moorland sur- 

 face waters often act strongly on lead, the reaction of the water is either 

 neutral or faintly acid, and the addition of a little chalk (carbonate 

 of lime) effectually destroys this solvent power. Such waters, how- 

 ever, are yielded by gravels which, on the Drift maps, are referred to 

 as " Glacial Drift," especially if such gravels occur on the tops of 

 hills, or far removed from any Boulder clay. Table II. contains 

 analyses of many waters containing little or no carbonate of lime, 

 and most of them can dissolve lead freely. Such waters occur at 

 Asheldham (an isolated gravel patch), Great Baddow, Little Baddow, 

 Danbury, Woodham Mortimer, and Woodham Walter, the gravel 

 upon which these parishes lie being far from any Boulder clay. At 

 Galleywood, Writtle, Fryerning, Ingatestone. and Stock, the Bagshot 



