28 THE SHALLOW AND DEEP WELL WATERS OF ESSEX. 



position of the well when the iVIemoir was published, and has consequently placed 

 the explanatory words " Valley Drift," against the details of the superficial brick- 

 earth and gravel. But he informs me that he has since discovered that the true 

 locality of the well-section is not Dagenham hut Dagnams, between three and four 

 miles north-east of Romford. The very great thickness of London Clay given as 

 existing at Dagenham, together with the round numbers " 400 feet," seemed to 

 me, last July, to suggest a want of perfect accuracy in the account. But as the 

 words " Valley Drift " applied to the superficial beds at Dagenham, and are 

 utterly inapplicable to those at Dagnams, which are more than 200 feet above 

 the sea, and as 200 feet of London Clay would have been enough for my purpose, 

 I thought I might safely quote this well-section. However, though it cannot be 

 mentioned as confirming the existence of the continuation of the long line of 

 synclinal fold spoken of in my little paper, nothing else there seems to me to 

 need any modification. — T. V. Holmes, February 23rd, 1893. 



Rainfall at Chelmsford in 1892. — Mr. F. Chancellor has recorded the 



ioUowing monthly summaries of the rainfall at Chelmsford as observed by 

 himself during 1892 : — Jarmary, 0-48 ; February, 2-42 ; March, i-o8 ; April, 

 I'2I ; May, o'Sy ; June, 2-64 ; July, 1-27 ; August, 3-52 ; September, 2-22 ; 

 October, 4-05 ; November, 2-09 ; December, 1-31 : Total, 23-16. 



THE SHALLOW AND DEEP WELL WATERS 

 OF ESSEX. 



By JOHN C. THRESH, D.Sc, !\LB., D.P.H. etc. 

 [Read, February ^ist, iSgj. 



C0NT£N7S. — Sources cf our Water Supplies — Variation in the character of 

 the water from various kinds of Gravel — Effect of a stratum of Boulder 

 Clay — Magnesian Waters — Deep] well waters (l) from Tertiary Sands 

 (2) from the Chalk — Great variation in character — Causes — Effect of 

 proximity to the Ocean, etc. 



The paper is written in the hope that Essex Geologists may be* able to explain sotne of 

 the author s difficulties, and that others may help by procuring for him samples 

 from certain districts not yet represented. 



npHE above somewhat hurriedly adopted title is probably not the 

 most appropriate one for the subject we have to discuss this 

 evening, and on that account our secretary acted wisely in giving my 

 short syllabus in the circular convening this meeting. 



During the past three and a-half years I find that I have 

 examined 874 samples of water from various portions of Essex 

 (by far the largest majority from the district around Maldon and 

 Chelmsford), the object, in every case, being to ascertain whether 

 they were sufficiently free from pollution and otherwise of such a 

 character as to be fit for drinking and domestic purpo.ses. About 

 two years ago, I published a " Report on the Water Supplies of the 



