REVERSIBILITY OF THE COLLOIDAL CONDITION OF SOILS 501 
TABLE 7. Apsorption oF WATER VAPoR BY AIR-DRIED, ARTIFICIALLY PREPARED, SoIL 
CoLLo1ps 
Per cent of water vapor adsorbed by 
Ferric oxide Alumina Humus Silica 
9.5+0.4 10.25+0.6 30.7+0.0 58.1+0.25 
Principal soils used 
Two surface soils and two subsoils were used in these experiments. 
These soils, consisting of Dunkirk surface soil, Clyde surface soil, Dunkirk 
subsoil, and Vergennes subsoil, represent a range of conditions. Their 
mechanical analyses, according to the centrifugal method of the United 
States Bureau of Soils, are given in table 8: 
TABLE 8. Mecuanicat ANALYSES OF PRINCIPAL Sorts Usep IN EXPERIMENTAL WoRK 
Divtalowis | CGE. inwaieiak || exams 
surface surface : 3 
] | subsoil subsoil 
SO ae Sor ( cent) | (per cent) 
(per cent) | (per cent) | ‘P°T P 
IRI® GREW! ts o Cain. bone OD Bee Oa ieee 0.170 0.145 0.000 0.020 
(CIDTMED Chitiel cc. do bis Cee Cle RIOR eee 0.305 1.055 0.260 0.045 
iMechtinn gainel, oooh sooo ee eee eB Nee 0.690 3.925 0.605 0.080 
Rime gail: 3), aoe an eee ae eee ere ee 2.270 9.895 1.145 0.735 
CT VATE TS AU Gry at Ney. cv slerdeiccc wavs sie 2 9.590 11.525 12.145 1.595 
Silt. £ wo ced eon O eee Sata eae er 74.030 53.330 65.800 22.960 
CIENT o oda d bbecio ere cues ae ea area Gs 12.945 | 20.125 20.045 74.565 
The Dunkirk surface soil was obtained from Caldwell Field, Cornell 
University. According to the textural classification (Lyon, Fippin, and 
Buckman, 1915) of the United States-Bureau of Soils, it is a silt loam. 
The sod was removed and the soil was taken from three to twelve inches 
below the surface. 
The Clyde surface soil came from another field on the university farm, 
and represents a phase of the Dunkirk series which is rich in organic 
matter. These soils are naturally poorly drained and are much darker 
in color than the soils of the Dunkirk series proper. In getting the sample 
the sod was removed, as in the case of the Dunkirk surface soil. Textur- 
ally the Clyde soil is a silty clay loam. 
