208 BULLETIN OF THE BUSSEY INSTITUTION. 
No. of The loams con- 
, ment Time of drying. Grms. CO;. solid. pose a, with Anita pr peswe ety 
oie. { two or three days 0.0332 0.210 0 2.63 %, 
onemonth. . . 0.0462 0.275 Distinct 1.57 
1. . § twoor three days 0.0292 0.160 0 0.58 
onemonth. . . 0.0700 0.285 Decided 1.26 
ur . § twoor three days 0.0325 0.150 0 2.20 
onemonth. . . 0.0200 0.820 0 1.10 
IV . two or three days 0.0037 0.085 0 0.95 
onemonth. . . 0.0050 0.700 0 0.57 
The reasons of the exceptional behavior of Nos. III. and IV. deserve to 
be carefully studied. No. III., it will be noticed, was a woodland earth 
rich in humus, and No. IV. a subsoil that was supposed to be well-nigh 
free from organic matter. It is probable that the explanation of the 
apparent anomaly will be found in the formation of organic acids in the 
earths, as has been insisted upon by Mulder; * and it may well be true that 
the formation of .such acids in times of drought is as characteristic for 
some kinds of soils as the formation of carbonic acid is for other kinds. It 
may,here be reiterated, that all the normal cultivable loams thus far ex- 
amined in this laboratory have shown an increase of carbonic acid on 
being kept, as indicated by the reactions of their percolates with am- 
monia water. 
Several trials were made to determine how the moist and recently 
dried loams would behave when percolated with carbonic-acid water, 
instead of pure water, and it appeared, in every instance, that the earth 
either decomposed the carbonic-acid water to a considerable extent, or 
in some way retained the carbonic acid in such wise that no increase 
of this substance could be detected in the percolate until an appreciable 
volume of the liquid had passed through the earth. For example: A 
quantity of earth was taken from the Plain-field, June 1, at a time that 
was neither wet nor dry, and placed immediately in a cylinder 7 X 
46 cm.; carbonic-acid water being then poured upon the top of the column 
of earth, 350 cc. of the liquid were absorbed by it before any drops 
began to fall; but no reaction for carbonic acid was obtained, by testing 
directly with lime water, until 300 cc. of percolate had been collected ; 
and 100 cc. more of the liquid passed through the earth before the 
percolate gave a reaction for carbonic acid that was comparable with 
that given by the carbonic-acid water itself, which had not been in con- 
tact with the earth. 
In one instance, where a similar column of fresh Plain-field earth 
had been percolated with pure water, of which 300 cc. were required 
* In his “ Chemie der Ackerkrume,” Berlin, 1863, 1. pp. 527, 445. 
