72 8S. W. Johnson on some points of Agricultural Science. 
In the older treatises on agronomy we find allusion made to 
the power of soils to absorb gases, yon ~ panes poi praily as 
exercised toward carbonic acid an as 
be of much agricultural A: Sn although the “tecle of 
precise experimental knowledge as to its extent, has been con- 
fessed and lamented. 
The absorptive power of the soil not only for odors and gases, 
but also for fixed matters carried into it in a state of solution, is 
illustrated in certain commonly occurring instances. Thus the 
wells in densely populated cities, or in the apo of barn-yards, 
or filthy canals, remain sweet and pure for a greater or less 
period of time, though they must be constantly x pe waters 
that have been in contact with putrefying animal m The 
filtration of the foullest water through a _ a vot ‘loamy 
earth remoyes all unpleasant effluvium a 
In the year 1850 it became known theopph two interesting 
nces, 
not toward hy drochloric, nitric and sulphuric aci 
ute solutions of hydrochlorate, nitrate, or su hate of am- 
quantity of soil, the salts are decomposed, the bases remain in 
insoluble combination with the tr and the acids are found in 
the solution united for the most part to lim 
Previous to 1850, the i ir oie of the soil was ex- 
“0 ained as a result ‘merely of the surface attraction of porous 
dies. Thus Liebig i in his “Chemistry applied to Agriculture 
Physiology,” referred the condensation of ammonia in soils, 
o the surface attraction of oxyd of iron, alumina and humus, 
and compared this power of soils to that aaa by charcoal, 
which absorbs 90 times its volume of ammonia gas, and evolves 
Th ing ters 
foul water hy contact with earth, has been consi idered ss 
a then 
sate by oxydation in the same manner as operated by charcoal and platinum 
ac On the absorbent Power of Soils.” By H. 8. Thomson. _Vol.-xi pp. 65-4; s=0 
On ta Powered Bebe howe Maes” By J. Thomas Way, Consulting Chem 
ist of the Roy. Ag. Society. Vol. xi, pp. 317-380; also, vol. xili, pp. 123-142. 
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