THE ANALYSIS OF VIRGIN SOILS. 359 



It will be noticed that this is a rather strongly calcareous soil, (nearly 

 9% of calcic carbonate), slightly impregnated with alkali, of which abouV 

 one-ninth is saltpeter. One portion of this soil was thoroughly leached 

 with distilled water until not a trace of nitrates could be detected in the 

 leachings. Another portion was treated for the removal of humus 

 according to the Grandeau method (see chapter 8, page 132) : the ex- 

 tracted soil showed under the microscope an abundance of vegetable 

 debris, some slightly browned as from incipient humification. 



The calcic and magnesic carbonates withdrawn in the humus-extrac- 

 tion were then restored to the soil in the form of finely divided pre- 

 cipitates and thoroughly mixed in, first in the dry and then in the wet 

 condition ; the extracted soil being repeatedly wetted with turbid water 

 from the leached soil, in order to replace and reinfect it with the nitri- 

 fying bacteria. Both soils were then spread out in flat glass dishes and 

 placed in a wooden box containing also a similar flat dish with distilled 

 water, upon which played the draught from the inlet pipe opening into 

 the outer air, with outlet-holes in the cover at the opposite end ; thus 

 keeping the air within fairly moist. In addition, the soils themselves 

 were moistened with distilled water every three days and restored to a 

 loose condition by stirring. The whole was placed so as to maintain, 

 during the greater part of the 24 hours, a temperature of from 30 to 

 35 degrees C. At intervals the samples of both soils were leached and 

 color-titrated for their nitrate content by the picric-acid test. The 

 results, calculated as sodic nitrate, during two years were as follows : 



It will be noted that in the course of four months, nitrification had 

 not sensibly set in in the extracted soil ; while in the leached natural 

 soil the nitrate-content had reached to three-fifths the amount originally 

 present, and in the course of a year the nitrate-content of the latter 

 was more than double that of the original (unleached) soil ; while that 

 in the extracted soil had only reached one-seventh of the same. At 

 the end of two years we find a still farther increase of nitric nitrogen in 

 both, the ratio between the two remaining about the same (i : 14). 

 At the same time the ratio of increase attained at first had materially 

 diminished in the water-leached soil, probably on account of the accumu- 

 lation of the niter itself. 



