On the Rain and Drainage - Waters at Rothamsted. 
11 
2. The Composition of the Drainage-Waters. 
The first investigation upon the composition of the drainage- 
waters from Broad balk Field was conducted by Dr. Voelcker. 
He examined in all five series of drain-waters, each collected 
when the drains were flowing largely, and including samples 
from nearly all the pipes. The collections were made on 
Dec. 6, 1866; on May 21, 1867; on Jan. 13, 1868; on 
April 21, 1868 : and on Dec. 29, 1868. The results of the 65 
analyses are given in detail in a paper " On the Composition of 
Waters of Land-Drainage.," communicated by Dr. Voelcker to 
this ' Journal ' in 1874, page 132.* 
In Table XL. we have recalculated into parts per million t 
the principal ingredients found in two of the most characteristic 
series of waters, and have also given the mean composition of 
the drainage from each plot, calculated from the whole of 
Dr. Voelcker's analyses.! The collection on Jan. 13, 1868, was 
the first considerable running after the application of the autumn 
manures ; the collection on April 21 was a later running in the 
same season, after the application of the nitrate of sodium to 
Plot 9. From want of space, the determinations of organic 
matter (by ignition), oxide of iron, carbonic acid, and silica 
are omitted. 
Dr. Voelcker's analyses are of special value, as they are the 
only ones giving a full account of the mineral constituents con- 
tained in the waters from the various plots. We shall, however, 
postpone the consideration of the results until we have the whole 
subject before us. 
The next examination of the Broadbalk waters was made by 
Dr. Frankland. He made in all 103 analyses, the collections 
extending from Jan. 13, 1868, to Feb. 26, 1873. Five of these 
* A Summary of the results was communicated by Dr. Voelcker to the 
Chemical Society in 1871 ; see Jour. Cliem. Soc. xsiv. 276. 
t We have given the whole of the analyses of rain and drainage-water in 
parts per million, partly because any smaller unit involves the use of long 
decimals, and partly because results thus expressed are equally intelligible to 
English and foreign readers; "parts per million" are indeed identical with the 
'' milligrams per litre," commonly employed on the Continent. For those 
English readers to whom a million may appear a vague term we may here state, 
that 1 inch of water per acre weighs 226,263 lbs., consequently 10 parts per 
million of nitrogen, lime, or any other constituent in a drainage- water, corre- 
sponds to a loss of 2 '26 lbs. per acre for each inch of drainage. 
% The mean composition of the drainage from Plot 2 is calculated from two 
analyses, that of Plot 15 from three analyses, tbe other means are calculated 
from live analyses. The potash and soda were determined only in the last four 
series of waters. Phosphoric acid was determined in the fourth series of waters, 
and partly in the second and third ; the means given are of two determinations, 
save in tlie case of Plots 7, 8, and 9, in which phosphoric acid was only deter- 
mined in the fourth series. 
