AND THE HERTFORDSHIRE BOURNE. 



83 



Appendix. 



Since the above -svas -written and read before the Society I have 

 been kindly favoured by Mr. Prancis, the present chief Engineer 

 to the New River Company, with particulars of the weekly How 

 of the Chad well Spring up to the time of its cessation, wliich is 

 shown by the gaui;ings to have been between the middle and end 

 of July, thus confiruung my conclusion that it must have ceased 

 to flow a considerable time before it was reported to have done so 

 about the beginning of September. 



This has enabled me to extend by two years the comparison of 

 the flow of the spring with the rainfall, bringing it up to the 

 31st of March, 1898. Taking the 23 years from April, 1875, to 

 March, 1898, in periods of 6, 6, 6, and 5 years, the result is as 

 follows : — 



The ratios are to the rainfall of 1842 to 1892 (April to March), 

 and to 3,600,000 gallons per day as the accepted mean flow of the 

 spring up to at least the year 1874. 



It is curious that the mean rainfall in the five years 1893 to 1898 

 should be exactly the same as that in the six years 1887 to 1893, 

 bat still more so that with a heavier winter rainfall in the later 

 period the flow of the Chadwell Spring should be much less than it 

 ■ft^as in the earlier period. It appears to me to prove that our Chalk 

 reservoir is being depleted by the excessive pumping from deep 

 wells, the plane of saturation in the valley of the Lea being 

 permanently lowered. 



Explanation of Plate I. 



In the foreground is the basin of the Chadwell Spring. Erected over it is 

 a centrifugal pump by means of which the water is kept at a lower level than 

 it would otherwise assume, so that the basin may be cleaned out, and part of one 

 side which had given way may be concreted. In the channel to the right a sluice 

 is being built to cut off the water of the Xew River whenever the spring may 

 fail. The temporary dam across the channel is a little further to the right. 

 In the distance is the Xew River, which flows out of the River Lea opposite 

 "Ware Park. Adjoining the White House on it (a tool -house) is a weir over 

 which any surplus water may flow into the Manifold Ditch, and thence, by the 

 Hertford sewage-efl3uent, buck into the Lea. The old marble gauge (now 

 disu>ieii) is seen a little to the right of this building. 



Tiie plate is from a photograph by Mr. Alfred Poore, of Hertford. 



