40 



J. HOPKIISrsON' HEETFOKDSHIKE RAINFALL, 



In the half-century ending 31st March, 1892, the wettest year 

 was 1852-53, mean rainfall 37'08ins. or 40 per cent, above the 

 average for the half-century (the average here being taken at 

 26-33 inches), the next was 1882-83, mean 34-77 ins. or 

 32 per cent, above the average; the driest year was 1854-55, 

 mean 19-33 ins. or 27 per cent, below the average; the next was 

 1870-71, mean 1970 ins. or 25 per cent, below the average. The 

 wettest two years in succession were 1875-76 and 1876-77, 

 mean 33-10 ins. or 26 per cent, above the average; the next 

 were 1859-60 and 1860-61_, mean 31-52 ins. or 20 per cent, 

 above the average; the driest two years were 1863-64 and 

 1864-65, mean 21-48 ins. ; the next were 1873-74 and 1874-75, 

 mean 21-69 ins , both about 18 per cent, below the average. The 

 wettest three years in succession were 1880-81 to 1882-83, mean 

 31-99 ins., and 1878-79 to 1880-81, mean 31-86 ins., both about 

 2 1 per cent, above the average ; the driest three years were 

 1844-45 to 1846-47, mean 22-58 ins., and 1862-63 to 1864-65, 

 mean 22-62 ins., both about 14 per cent, below the average. 



Percolation and Evaporation. 



Tables XII to XIY have been compiled from tables published 

 in the ' Proceedings of the Institution of Civil Engineers,' but for 

 the purpose of this inquiry they are in a totally different form 

 from that of the original tables, and they give results which can 

 only be derived from them by calculation. Tables XII and XIII 

 give results of experiments made by Messrs. Dickinson & Co., 

 at Xash Mills, on percolation through chalk and soil with grass 

 growing on the surface. Tables XIY and XV give results of 

 experiments made by Mr. Charles Greaves, at Lea Bridge, on 

 percolation through soil with gi'ass growing on the surface, and 

 on evaporation from the surface of water in a tank moored on 

 a flowing stream. And Table XVI gives results of experiments 

 made by Messrs. Lawes and Gilbert, at Rothamsted, on percolation 

 of rain through soil with the surface kept free from vegetation. 



Erom Table XII, which gives the percolation through 3 feet of 

 chalk with grass growing on the surface, at Xash Mills, for the 

 thirty years ending 31st March, 1884, and the difference from 

 the rainfall, considered as evaporation, the following general results 

 may be deduced : — 



