202 Oil the Rain and Drainatje - Water s at Rothamsted. 
of their classification into summer and winter periods is gene- 
rally consistent and full of interest. In every case the amount 
of total solid matter dissolved in the rain-water is considerably 
greater in summer than in winter. In a majority of cases the 
ammonia is greater in summer than in winter. The nitric 
acid is also in every case greatest in summer-time, though the 
figures are very irregular, owing to the small number of analyses 
at command. The general distribution of ammonia and nitric 
acid is thus the same as that shown in the earlier analyses of 
Rothamsted rain-water. 
The most striking difference in the two seasons occurs in the 
organic matter. The total organic matter is in a majority of 
cases greater in summer than in winter ; its composition, how- 
ever, is quite distinct. In summer the carbon is generally 
greater than in winter, while the nitrogen in summer is less 
than in winter. The proportion of nitrogen to carbon is thus 
A'ery different at the two seasons of the year, as will appear 
more clearly from the following Table : 
Table XIV. — Average proportion of Organic Nitrogen to Carbon 
in Rainfalls of different Amount, and collected at different 
Seasons of the Year. 
Quantity of Rainfall. 
Summer. 
Winter. 
Whole Year. 
1 : 6-4 
1 : 3-4 
1:4-5 
Between • 10 and • 20 inch 
1 : 6-5 
1 : 3-7 
1:5-3 1 
Between '20 and "40 inch 
1 : 6-8 
1 : 2-9 
1:5-3 
Between '50 and "90 inch 
1 : 8-8 
1 : 2-7 
1:5-8 
The simplest explanation of these facts seems to be that in 
summer-time the organic matter in rain-water contains a larger 
proportion of fresh vegetable matter than in winter ; in the 
latter season the organic impurity must consist chiefly of 
products of decay. 
The arrangement of the few analyses of dew and hoar-frost 
in summer and winter groups shows, as in the case of rain, a 
preponderance of total solid matter, of organic matter, and 
of ammonia, in the summer months, but the series is too small 
for detailed discussion. 
Dr. Frankland has paid considerable attention in his Report 
to the influence of various winds on the composition of the 
rain-water collected at Rothamsted. The question obviously 
presents considerable difficulty. To compare under equal con- 
ditions the rain produced by different winds, we must clearly 
