338 
On the Rain and Drainage - Waters at Rotliamsted. 
of nitric acid and of chlorine have been made as soon as 
possible after the completion of the monthly sample. It is 
obvious that the analyses of the earlier samples do not possess 
the same quantitative value as those more recently done ; we 
shall give, however, in a separate table (XXXII.) the amounts 
of nitrogen as nitric acid found in the best preserved samples 
in the earlier series, as they serve to illustrate some facts con- 
nected with these drainage-waters. The nitric acid has in all 
cases been determined by the improved indigo method (' Trans. 
Chem. Soc.,' 1879, p. 578), and the chlorine by the volumetric 
method already noticed. 
Table XXXII. — Nitkogen as Nitric Acid in some Mixed 
Monthly Samples of Drainage- Water from the three Drain- 
Gauges, 1874-77. 
Months. 
Drainage in Inches. 
Nitrogen as Nitric Acid per 
Million ot Water. 
20-Inch 
Gauge. 
40-Inch 
Gauge. 
60-Inch 
Gauge. 
20-Inch 
Gauge. 
40-Inch 
Gauge. 
60-Inch 
Gauge. 
1874. 
0 
634 
0 
249 
0 
212 
25 
5 
20-0 
15-1 
1 
525 
1 
258 
1 
024 
39 
6 
30-5 
22-5 
1 
209 
1 
045 
0 
687 
20-0 
1 
155 
1 
340 
1 
039 
23-2 
1875. 
0 
349 
0 
262 
0 
140 
25 
1 
23-5 
22-5 
3 
292 
3 
661 
3 
346 
26 
1 
21-6 
22-8 
0 
001 
0 
025 
0 
030 
20-9 
23-8 
0 
890 
0 
829 
0 
707 
38 
3 
26-7 
25-9 
1870. 
1 
283 
1 
745 
1 
585 
9 
3 
10-9 
14-6 
1 
360 
1 
664 
1 
720 
11-5 
12-2 
0 
146 
0 
141 
0 
025 
22 
0 
18-7 
2 
296 
2 
236 
2 
041 
25 
2 
19-8 
5 
212 
5-741 
5 
252 
9 
8 
10-0 
11-5 
1877. 
January — April 
7 
003 
8 
467 
7 
930 
8 
1 
91 
12-0 
The drain-gauges did not run during June and July 1876, 
and to a scarcely appreciable extent in May of the same year. 
Two facts are pretty clearly shown by these somewhat dis- 
connected determinations. 1. That the maximum richness in 
nitrates occurs in the early autumn drainage, the proportion 
tliminishing through the winter, and reaching a minimum in 
