ABSORBENT POWER OF SOILS. 171 
odor, by burying them for a few days in the earth. The 
Indians of this country are said to sweeten the carcass of 
the skunk by the same process, when needful, to fit it for 
their food. Dogs and foxes bury bones and meat in the 
ground, and afterward exhume them in a state of com- 
parative freedom from offensive odor. 
When human excrements are covered with fine dry 
earth, as in the “ Earth Closet” system, all odor is at once 
suppressed and never reappears. At the most, besides an 
“earthy” smell, an odor of ammonia appears, resulting 
from decomposition, which appears to proceed at once to 
its ultimate results without admitting of the formation of 
any intermediate offensive compounds. 
Dr. Angus Smith, having frequently observed the pres- 
ence of nitrates in the water of shallow town wells, sus- 
pected that the nitric acid was derived from animal mat- 
ters, and to test this view, made experiments on the action 
of filters of sand, and other porous bodies, upon solutions 
of different animal and vegetable matters. He found 
that in such circumstances oxidation took place most rap- 
idly—the nitrogen of organic matters being converted in- 
to nitric acid, the carbon and hydrogen combining with 
oxygen at the same time. Thus asolution of yeast, which 
contained no nitric acid, after being passed through a 
filter of sand, gave abundant evidence of salts of this acid. 
Colored solutions were in this way more or less decolor- 
ized. Water, rendered brown by peaty matter, was found 
to be purified by filtration through sand.* 
g 5 
POWER OF SOILS TO REMOVE DISSOLVED SOLIDS FROM 
THEIR SOLUTIONS. 
Action of Sand upon Saline Solutions.—It has long 
been known that simple sand is capable of partially re- 
* This account of Dr. Smith’s experiments is quoted from Prof. Way’s paper 
“On the Power of Soils to Absorb Manure.” (Jour. Roy. Ag. Soc. of England, 
XI, p. 317.) 
