24 Rev. A. Irving — Water Supply from the BagsJwt Beds, etc. 



with such materials much vegetable debris should have been brought 

 in some instances from the adjacent land-surfaces, or accumulated 

 from the decay of aquatic and marsh plants in the well-known 

 process by which lakes are often filled up with sandy and peaty 

 matter. The twelve feet of sand in the section at Brackley may 

 represent the ' Midford Sands,' the ' Cephalopoda Bed ' of the Cots- 

 wold country being absent in this part of England, Whatever their 

 history, it is their petrological character which concerns us here. 



3. At Evenley, about a mile from Brackley, there is a well thirty 

 feet deep, which receives its water from the strata of the Great 

 Oolite, and this water is contaminated by vegetable-matter in solu- 

 tion. This is proved, not only by the direct precipitation of crenic 

 acid from the water in considerable quantity, according to the method 

 given (from Berzelius) in Watts' Dictionary of Chemistry, but also 

 by the presence of a high percentage of albumenoid ammonia, while 

 there is the merest trace of free ammonia, and the amount of chlorine 

 is very small, not more than 1-3 grs. per gallon.^ It should be added 

 that the water of this well was examined, when it had an unusually 

 strong smell betokening vegetable pollution, soon after the heavy 

 rains, which followed upon the long period of drought experienced 

 in the early part of the summer of last year. In this case too the 

 water has been found caj^able of purification by the process, to which 

 I have referred above. This well probably penetrates a dirty bed, 

 such as was passed through in the Brackley well at a depth of from 

 thirty-one to forty-one feet, interbedded with the limestones and 

 marls of the Great Oolite. One fact in connexion with the water of 

 this well puzzled me for a time : the water, when heated and drawn 

 from the kitchen-boiler, was not discoloured in the slightest degree 

 by iron, as is the case with soft water contaminated by vegetable- 

 matter in solution. This was ultimately explained by the fact that 

 the calcareous hardness of the water has produced a lining of carbo- 

 nate of lime, owing to the decomposition by heat of the bicarbonate, 

 which the water brings in solution from the Oolitic strata. The 

 failure of the vegetable acids in this case to take up iron results 

 therefore from the fact of non-contact between the water and the 

 iron. The fact throws additional light upon the theory of Mr. 

 Brande and others, on which some remarks have been made above. 



In the light of our present knowledge we may hazard a provisional 

 generalization, which will lead us to look for vegetable contamination 

 in many cases of water drawn from such levels as are marked by 

 any considerable break in the normal succession of the strata ; such, 

 for example, as that which occurs so often all down through the 

 Vale of Wardour, and down to the coast of Dorsetshire, the 

 Cretaceous series resting unconformably upon various members of 

 the Mesozoic strata, down even to the Trias, 



We must return for a further brief consideration of the Bagshot 



strata. In the pursuance of my observation upon these strata in 



East Berksliire, the conviction has gradually grown up in my own 



mind, that the relative distribution of the different members of that 



^ Comp. Wanklyn's Water Analysis, 5tli ed. 1879, p. 49, 



