22 Rev. A. Irving — Wafer Supply from the BagaJiot Beds, etc. 



Tims far our consideration has been almost entirely confined to 

 the Bagshot strata and the water furnished by them. Pollution of 

 water by vegetable-matter in solution is not, however, confined to 

 these strata, or even to strata of Tertiary age. All the way down 

 the Secondary Series conditions of a similar nature recur at intervals 

 and in different areas : in fact, it is to the later Palaaozoic Rocks 

 that we have to go to find in the Coal-measnres the maximum of 

 vegetable debris sealed up in the sedimentary strata. Of course in 

 the coal-seams carbonization has proceeded to a greater extent, and 

 the remains of ancient vegetation are presented to us in a more 

 massive form ; but between the two extremes there are many 

 degrees, and it seems quite impossible to assign any limits to the 

 time, even in a geological sense, that vegetable debris may remain 

 undestroyed, if it is sealed up hermetically in the strata of the 

 earth's crust, and thus protected from the action of atmospheric 

 oxygen. Several instances of water drawn fi-om various horizons 

 in the Secondary rocks and at the same time highly charged with 

 vegetable acids in solution, have come before my notice within the 

 past year. 



1. Some time ago my attention was drawn to three wells in the 

 Wallingford district which draw water from the strata below the 

 Chalk. One of these is the new well at the Lunatic Asylum at 

 Moulsford, the other two are in the town of Wallingford. The water 

 from one of the latter is loaded with vegetable-matter in solution, 

 especially in the form of crenic acid ; the other two wells are pretty 

 free from it. A comparison of the sections of the three wells, which 

 I have been able to make through the courtesy of Messrs. Le Grande 

 and Sutcliffe, of Bunhill Fields, who bored the wells, shows that 

 the well which yields water heavily charged with crenic acid, etc., 

 passes through a stratum of dirty dark-green sand, which is altogether 

 wanting in the other two sections. This sand has the character of 

 those impure Bagshot Sands of which I have already said a good 

 deal, and the water drawn from the well is polluted just in the same 

 way as water drawn from the Middle and Lower Bagshot strata is 

 contaminated. No fossils turning up, it is not easy to determine the 

 exact horizon from which the water of these three wells is drawn. 

 The section of the well which yields impure water is as follows : — 



1. Sand and gravel (river alluvium) ) ft. in. 



2. Clay, light blue and loamy > about 22 



3. Hard light grey rock (Upper Greensand) ) 



4. Stiff grey clay (Gault) 20 



6. I)ork green sand 6 



6. Hard rock (sandstone) 2 



Total 44 6 



Comparing this with the description given by Prof. Phillips ^ of 

 a section at Culham not very many miles distant, it seems extremely 

 likely that the ' hard rock ' or sandstone pierced by this well for 

 two feet at the bottom is none other than the sandy cap of the 

 Kimmeridge Clay, and that the Lower Greensand is represented in 

 ^ Vide Geology of Oxford and the Valley of the Thames, p. 427. j 



