266 On the Main and Drainage - Waters at Rothamsted. 
average proportion for the six winter months is 2-70, and for 
the six summer months 1-06 per million, or less than one-half 
the winter proportion. This striking difference between the 
amount of chlorine in the summer and winter rainfall is not 
shown in Dr. Frankland's analyses of the Rothamsted rain- 
water. We have, however, already noticed that the series of 
samples analysed by him was not well suited for the exhibition 
of summer and winter characteristics. The cause of the excess 
of chlorides in the winter rain is probably to be found in the 
more stormy character of this season, and perhaps also in the 
coal smoke which then affects the atmosphere. 
We must not conclude our remarks on the composition of 
rain-water without a very brief glance at the results of other 
experimenters. 
The best idea of the variations which may occur in the com- 
postion of rain-water from the different degrees of impurity in 
the atmosphere from which it is collected, is afforded by the 
researches of Dr. Angus Smith (' Air and Rain ; the begin- 
nings of a Chemical Climatology,' 1872). In this work will 
be found the results of numerous analyses of rain-water, col- 
lected both from country districts and towns in the United 
Kingdom. The average results obtained for a few districts 
are given in the following Table : 
Table XVII. — Average composition of Samples of Rain from various 
districts of England and Scotland, in parts per Million. 
DiSTEICT. 
Nitrogen as 
Clilorine. 
Sulpliuric 
Ammonia. 
Nitric Acid. 
Acid. 
England, country places, 
inland .. 
0-88 
0-19 
3 '88 
5-52 
4-25 
0-22 
8-46 
34-27 
Scotland, country places, 
sea-coast 
0-61 
0-11 
12-24 
5-64 
»> )) )7 
inland 
0-44 
0 08 
3-28 
2-06 
3-15 
0-30 
5-70 
16-50 
„ Glasgow 
7-49 
0-C3 
8-72 
70-19 
The amounts of ammonia and nitric acid in the rain from 
" country places," are seen to be similar to those found in the 
Rothamsted rainfall. In the rain of towns there is a very 
large increase bcjth in ammonia and sulphuric acid, and a 
smaller, though considerable, increase in chlorides and nitrates. 
