66 
On the Rain and Drainage - Waters at Rothamsted. 
SUMMARY. 
Amount and Composition of Rainfall. 
1. The rainfall at Rothamsted during 28 years, 1853-80, has 
varied from 18"56 inches in 1864 to 36'04 inches in 1879, the 
average being 28"30 inches. 
2. Determinations of ammonia at Rothamsted in the rain of 
1853-4 showed an average of 0"74 nitrogen per million ; deter- 
minations by Way (1855 and 1856) 0*88 and 1'18 nitrogen per 
million. Frankland's determinations in 1869-70 showed 0'37 per 
million. Determinations made quite recently at Rothamsted 
confirm Frankland's results ; the earlier figures are probably 
too high. 
3. The total nitrogen supplied in the annual rainfall at 
Rothamsted is probably 4 to 5 lbs. per acre, excluding the con- 
densation by the soil. The mean of continental estimates, 
including localities near towns, is 10"23 lbs. per acre. 
4. The chlorine in Rothamsted rain has averaged 13'421bs., 
equal to 221'_i lbs. pure common salt per acre per annum. At 
Cirencester the amount is equal to 53'66 lbs. of salt. 
Deainage-water from Land Unmanueed and Uncropped. 
5. The annual drainage during 10 years, 1870-1 to 1879-80, 
from three drain-gauges, of heavy loam with clay subsoil in 
natural condition of consolidation, 20, 40 and 60 inches deep, 
has varied from 4-97 to 25'86 inches, mean 13'49 inches, or 
21*7, 60-5, and 43-4 per cent, of the rainfall. 
6. The evaporation from the bare soil averaged 5*58 inches 
from October to March, and 11*97 inches from April to Sep- 
tember, total 17"55 inches. The evaporation during the sum- 
mer and whole year is a fairly constant quantity with great 
differences of rainfall. 
7. The evaporation from a cropped soil is far more consider- 
able, and very variable. 
8. Nitrates are largely produced in soil by the action of a 
living ferment on the nitrogenous organic matter and am- 
monia ; nitrification takes place chiefly in the upper layer of soil, 
and is greatly favoured by the presence of water, and by summer 
temperature. The waters from the drain-gauges are richest in 
nitrates in late summer and autumn, and poorest in spring. 
9. The quantity of nitrogen as nitrates annually removed in 
the drainage-waters (October to September) has varied from 
31"78 lbs. to 57"95 lbs. per acre; the average of four years, 
