502 A. B. BraAUMoNnT 
The Dunkirk subsoil was taken at a depth of from one to two fee 
directly beneath the surface soil of the same series mentioned above. It 
is a silty clay loam texturally. 
The Vergennes subsoil was obtained from Washington County, New 
York. Like the soils described above, it is a glacial lake soil, and, up to 
1911 at least, 1t was the heaviest soil mapped by the United States Bureau 
of Soils. The sample was taken at a depth of from one to two feet. Tex- 
turally the soil is a clay. 
The organic matter and the humus content of these soils are given in 
table 9. These were determined according to the official methods 
described in Bulletin 107 of the United States Bureau of Chemistry, with 
the exception that ammonium carbonate was used to flocculate the clay 
in the ammonia extract of humus as suggested by Rather (1911). 
TABLE 9. Organic Marter (Loss spy Ienrtron) AND Humus or Principat Sorts Usep 
IN HXPERIMENTAL WorRK ; 
t 
Organic 
Soil aria Humus 
(per cent) (per cent) 
TD AON esate sents bheaitc Vole vep UR eae a ANI aM ea ee IN Uren Ei LONE ference eds 5.085 1,265 
@ly dersuriace ssi 2) PA NNR EM Tr MTAC Ra AEs oe AIR ae tr HO eee a 14.540 4.340 
Dunkirk subsoil acy cea ahs a ee Le iere a hl cular Gl alate aloaire an eae 3.055 0.205 
Vergennes sulosoile 7520) Sano ie SURO BIN Pea MLA iimaa On sar ee Rear 5.795 0.495 
Preparation of samples.— After the soils were brought to the laboratory 
they were dried to a condition in which they could be worked readily 
without sticking, and then put thru a 2-millimeter sieve. Each lot of soil 
was then thoroly mixed before samples were selected for individual treat- 
ments. Certain lots were kept moist thruout the experimentation by 
placing them in air-tight jars; other lets were subjected to air-drying at 
room temperature and at 105° C.—the former being designated as azr- 
dried and the latter as oven-dried. 
The air-dried samples were usually dried by spreading the soil out in 
enameled pans in layers about + inch deep. A layer of soil as thin as 
this usually dries very quickly. In case of alternate wetting and drying, 
the wetting was done with distilled water. No attempt was made to 
bring the soils to a definite moisture content; this was thought not worth 
