1 2 AV. AVHITAKEK — ADDRESS : 



We have an example of this change of composition in the 

 mineral matters of Chalk water just beyond our county, from 

 which county, however, the water is derived, for Mr. J. Francis 

 writes to me, concerning the wells of the New River Company, 

 that ' ' analyses show that in the case of those of our wells that 

 are nearer London and under a considerable depth of the 

 Tertiaries, the water is certainly more alkaline than in those 

 of the open Chalk." 



Some ten years ago the subject came before me in the pre- 

 paration of a Geological Survey Memoir, and I tried to account 

 for it. The only explanation which I could give, and somewhat 

 doubtfully, was that through communication between the Chalk 

 and the overlying Tertiary sands some of the salts in the latter 

 had been dissolved ou)(jinto the water. I am still inclined to think 

 that this idea is not wholly without foundation ; but doubt whether 

 it is enough to account for the facts. 



Soon after the publication of my Memoir I became aware of 

 a paper published two years earlier, wherein a better explanation 

 is given, and to this paper your attention will now be drawn. It 

 was written by one of the distinguished chemists who have worked 

 in the Eothamsted Laboratory, and who still dwells in the county.* 

 Although this paper is now more than ten years old, I fear that 

 others may be ignorant of it, as I was for a time, and, indeed, 

 I have found that few geologists or engineers know of it; one 

 may, therefore, quote from it with all the more reason. 



After an elaborate investigation of the well-waters of Harpenden, 

 Mr. Warington compares his results with those from other wells, 

 and he finds that the minimum of chlorine in the water of the 

 Harpenden wells is rarely reached in 111 other analyses. As 

 many of these were of high-class waters, he says "it would appear 

 that there is some peculiarity in the chalk water of Harpenden so 

 far as its contents in chlorides is concerned. I venture to think 

 that the low proportion of chlorides in the pure well waters of 

 Harpenden may be due to the situation of the village not far from 

 the escarpment of the chalk at the northern edge of the Thames 

 basin. The chalk here being at a considerable elevation .... and 

 the gradient of the underground water level very considerable, the 

 chalk rock has been in the course of ages washed very thoroughly 

 by the percolation of rain, and the chlorides originally present in 

 the rock when upheaved from the sea have been almost completely 

 removed. The wells of the lower part of the chalk basin are 



* "A Contribution to the Study of Well Waters," by E. Wariugton, F.R.S.: 

 ' Jouru. Chciu. Soc.,' vol. li (1687), p. 500. 



