AQUEOUS SOLUTION OF THE SOIL. 317 
ranging from 2 to 6 parts in 100,000 of soil.. (Jahresbe- 
richt der Ag. Chem., 1865, p. 84.) 
It should be remarked that Knop’s failure to find phos- 
phoric acid may depend on the (uranium) method he em- 
ployed, a method different from that commonly used. 
Can the Soil-water supply Crops with Food ?— As- 
suming, then, that all the soil-food for plants exists in solu- 
tion in the water of the soil, the question arises, Does the 
water of the soil contain enough of these substances to 
nourish crops? In case of very fertile or highly manured 
fields, this question without doubt should be answered af- 
firmatively. In respect of poor or ordinary soils, how- 
ever, the answer has been for the most part of late years 
in the negative. While to decide such a question is, per- 
haps, impossible, a closer discussion of it may prove ad- 
vantageous. 
Russell (Journal Highland and Ag. Soc., New Series, 
Vol. 8, p. 584) and Liebig (Ann. d. Chem. u. Pharm., CV, 
138) were the first to bring prominently forward the idea 
that crops are not fed simply from aqueous solutions. Dr. 
Anderson, of Glasgow, presents the argument as follows 
(his Ag. Chemistry, p. 113): 
“Tn order to obtain an estimate of the quantity of the 
substances actually dissolved, we shall select the results 
obtained * by Way. The average rain-fall in Kent, where 
the waters he examined were obtained, is 25 inches. Now, 
it appears that about two-fifths of all the rain which falls 
escapes through the drains, and the rest is got rid of by 
evaporation.+ An inch of rain falling on an English acre 
weighs rather more than a hundred tons; hence in the 
course of a year, there must pass off by the drains about 9 
1,000 tons of drainage water, carrying with it, out of the 
reach of plants, such substances as it has dissolved, and 
* On drain-waters, eee p 318. 
‘+ From Parke’s measurements, Jour. Roy. Ag. Soc., Hng., Vol. XVIL, p. 127%. 
