318 On the Rain and Drainage- Waters at Rothamsted. 
Table XXII. — The Average Monthly Eainfall, with the Average 
Monthly Peuoolation and Evaporation from Soil 20, 40, and 
60 Inches in Depth, during 10 Years, 1871-80. 
Drainage. 
Evaporation. 
Rainfall. 
Soil 
Soil 
.Soil 
Soil 
Soil 
Soil 
20 Inches 
40 Inches 
60 Inches 
20 Inches 
40 Inches 
60 Inches 
, 
Deep. 
Deep. 
Deep. 
Deep. 
Deep 
Deep. 
Inches. 
Inches. 
Inches. 
Inches. 
inches. 
Inches. 
Inches. 
January 
2 
802 
L UUO 
rt . on 1 
L UoU 
(\ • Tfli: 
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\) OUo 
Febniaiy . . 
2 
100 
1-401 
1-536 
1-378 
0-699 
0-564 
0-722 
March 
1 
595 
0-540 
0-675 
0-585 
1-055 
0-920 
1-010 
April . . 
2 
398 
0-810 
0-921 
0-852 
1-588 
1-477 
1-546 
May . . . . 
2 
224 
0-422 
0-501 
0-433 
1-802 
1-723 
1-791 
June 
2 
663 
0-521 
0-535 
0-486 
2-142 
2-128 
2-177 
July . . 
3 
280 
0-890 
0-918 
0-804 
2-390 
2-362 
2-476 
August * 
2 
677 
0-670 
0-663 
0-609 
2-007 
2-014 
2-068 
September .. 
3 
123 
1-170 
1-044 
0E27 
1-953 
2-079 
2 -190 
October 
3 
162 
1-694 
1-682 
1-414 
1-468 
1-480 
1-748 
November . . 
3 
094 
2-158 
2-241 
1-999 
0-936 
0-853 
1-095 
December . . 
2 
333 
1-758 
1-906 
1-724 
0-575- 
0-4-27 
0-609 
Whole Year 
31 
451 
14-040 
14-916 
13-241 
17-411 
16-535 
18-210 
during the ten years of the drainage experiments has been 
singularly abnormal ; not only has the annual fall been exces- 
sive (about 3 inches above the average), but the distribution 
has been irregular, certain months having been specially affected. 
If we assume, as we fairly may, that the amounts of monthly 
evaporation ascertained for the past ten years would remain 
nearly the same under a normal rainfall, it becomes possible by 
simply subtracting the excess, or adding the deficiency of the 
rainfall, to calculate what would be approximately the monthly 
drainage under a rainfall of average amount. The results of 
such a calculation will be found in Table XXIII. 
It should be stated that in the construction of this artificial 
Table (XXIII.), exceptional rainfalls and drainage, such as 
those of August 1879, are not excluded. The figures as they 
stand would indicate that under a normal rainfall considerable 
drainage would not set in before October, and would continue 
to the end of February, the maximum drainage being in January. 
From March to the end of September the amount of drainage 
is comparatively small, the minimum being reached in June and 
July. If these indications should prove to be correct, the 
natural drainage year of this uncropped land would commence 
with October, the first autumn month in which a great fall of 
temperature occurs, and also the month of maximum rainfall. 
* Excluding the very exceptional rainfall and drainage of August 1879, the 
average drainage for the month would be only about one-third as much as the 
figures show. 
