74 J. HOPKINSON — THE CHADWELL SPEING 



declining, and I fear permanently. Its average annual flow is 

 now about 40 per cent, less than it was 20 years ago, its yield 

 being about a million and a half gallons a day less tban it was tlien. 

 The period for which returns of the monthly and annual yield of 

 the spring are available is from January, 1875, to April, 1896. 

 (See Appendix.) Dividing the 20 years ending 31st March, 1896, 

 into four periods of five years each, the yield of the spring was as 

 follows: — in the first lustrum, 3,609,600 gallons a day; in the 

 second, 3,025,467; in the third, 2,785,184; and in the fourth, 

 2,328,294. If the 21 calendar years 1875-95 are divided into 

 three periods of seven years each, the mean flow of the spring 

 comes out thus: — in the first period, 3,603,000 gallons a day; in 

 the second, 2,900,500; and in the third, 2,485,888. The mean 

 flow for the whole of the 21 calendar years was 2,996,200 gallons 

 per diem. 



In 1852 Mr. C. W. Mylne, Engineer to the New Kiver Company, 

 stated that in his 40 years' experience he had never known the 

 Chadwell Spring to yield less than 2,600,000 gallons per diem, 

 a minimum considerably in excess of the present average yield. 



In 1857 Mr. James Muir, who succeeded Mr. Mylne as Engineer 

 to the New Kiver Company, stated that the minimum gauged, as 

 given by Mr. Mylne, was "a rare occurrence indeed," that the 

 average was 3,600,000 gallons per diem, and that the yield in 

 the beginning of that year was 6,300,000 gallons per diem. 



In 1867 Mr. Muir gave the minimum yield which he could 

 permanently rely upon as 3,200,000 gallons per diem, the daily 

 average as 3,600,000, and the average yield in 1866 as 4,500,000 

 gallons per diem. 



These are statements made before Royal Commissions or 

 Parliamentary Committees, and in 1874 the Eivers' Pollution 

 Commission, from the above and other evidence, came to the 

 conclusion that the minimum yield had up to that time been 

 2,592,000 gallons per diem, and the maximum, 6,336,000, and 

 estimated an average of 4,500,000 gallons per diem, but the only 

 value attaching to this estimate is that the spring was then so 

 powerful that it could have been seriously entertained. It shows 

 the fallacy of deducing the average from the extremes, and we 

 must fall back upon the average of 3,600,000, as given by 

 Mr. Muir, and never questioned until 1892. 



This, it will be seen, was about the average during the five years 

 1876-81 (April to March), and it was maintained to the early part 

 of the year 1884. It might be inferred that there was nothing 

 going on then to detrimentally affect the volume of the spring, did 

 we not take the rainfall into consideration. During these five years 

 the winter rainfall was 8 per cent, above the average for the half- 

 century 1842-92, and the yearly rainfall 18 per cent, above it. 

 With this heavy rainfall, aggregating 24 inches above the average, 

 or nearly six years' average rainfall in five years, the Chadwell 

 Spring gives a normal yield. In the five years 1881-86 the winter 

 rainfall was 12 per cent, above the average, and the yearly 



