On the Bain and Drainage-Waters at Rothamstcd. 325 
Table XXV. — Mu. Gkeaves's Results respecting Duaunage and 
Evaporation, average of 14 Years, 1800-7;'. 
January .. 
February 
March 
April 
M;iy 
June 
July 
August .. 
September 
October . . 
November 
December 
Rainfiill. 
Inches. 
2 870 
■596 
•93G 
•428 
•05G 
•205 
•774 
332 
•347 
•730 
•021 
•422 
Drainage. 
Sand. TurfcdSwil. 
Inches. 
2 •734 
1-524 
1-005 
1-117 
1-G5G 
572 
212 
■783 
■737 
•402 
-963 
2-173 
Inches. 
2-021) 
1-085 
0-879 
0-275 
0-105 
0-156 
0-013 
0-113 
0-071 
0-515 
0-833 
1^508 
Evaporation. 
Sand. Turfed Soil. Water. 
Inches. 
0^I3G 
0 072 
0-334 
0^311 
0^4()0 
0^633 
0^562 
0^549 
O^GIO 
0 - 328 
0-058 
0-249 
Inches. 
0-841 
0- 511 
1- OGO 
1-153 
1- 951 
2- 049 
1^7Gl 
2^219 
2 ••276 
2-215 
1^188 
0-914 
Whole Year.. 25-720 21-478 | 7-582 i 4-242 ! 18-138 
Inches. 
-761 
-603 
■065 
•098 
-753 
-142 
-443 
-850 
•606 
•056 
•707 
-574 
20-G58 
;ind but little water is evaporated from the surface even in the 
height of summer. In the whole year the quantity calculated as 
evaporated amounts to but 4-242 inches. The true amount of 
evaporation is probably, however, greater than this, as it is not 
very uncommon for the drainage from this gauge to exceed the 
rainfall, owing, as Mr. Greaves supposes, to condensation of 
water directly from the atmosphere. This excess of drainage 
over rain occurs most frequently in January and February. 
On the turfed soil the amount of evaporation from January to 
March is very similar to that observed on the bare soil at 
Rothamsted ; but from April to September — the growing season 
of the grass, — practically no drainage takes place, nearly the 
whole of the rainfall being evaporated. Drainage-water was 
indeed collected in July and August only on two, in June on 
three, and in May and September on four occasions during the 
fourteen years. The average amounts of water evaporated from 
the turf during summer, winter, and the whole year, namely, 
11'409, 6'731, and 18*138 inches, are very similar to those 
noted at Rothamsted ; they are so, however, simply from the 
very moderate amount of rainfall supplied to the soil. In the 
wet summer of 1860, 15"608 inches were evaporated by 
the turf in six months ; and in the wet season of 1872, the 
evaporation during twelve months reached 25'141 inches. 
There is thus but little constancy in the amount of evaporation, 
which depends largely on the amount of rainfall, and on the 
activity of the vegetation. With a heavier rainfall we should 
doubtless obtain more constant figures. 
