35ft HOW CROPS FEED. 



and on the "Changes which Liquid Manure undergoes in 

 contact with different Soils of Known Composition" {idem 

 XX., 134-57), he found, in seven experiments, that dung 

 liquor, after contact with various soils, lost or gained acid 

 ingredients, as exhibited l)y the following figures, in grains 

 per gallon : (loss is indicated by — , gain by +) : 



1 2 34567 A. B. 



Chloride of Potassium — S.Sl +9.17 —2.74 +2.14 —2.74 +2.55 —1.10 



Chloride of Sodium. . .—3.05 —2.43 —7.04 —1.12 —1.10 —1.24 +3.CG -1.89 +19.05 



Sulphuric Acid +3.32 —4.21 —1.06 —1.21 —0.27 +1.24 +3.44 +2.26 —0.42 



Silicic Acid +1.63 +10.33 —1.64 +0.72 +2.76 —0.11 —0.07 undet. —1.57 



Phosphoric Acid — — —4.23 —3.09 —2.91 —3.38 —0.13 —8.76 —7.71 



We notice that chlorine was perceptibly retained in 

 three instances, while in the other four it was, on the 

 whole, dissolved from the soil. Sulphuric acid was re- 

 moved from the solution in four instances, and taken up 

 by it in three others. In four cases silica was absorbed, 

 and in three was dissolved. In his first paper. Professor 

 Way recorded similar experiments, one with flax-steep 

 liquor and a second with sewage. The results, as regards 

 acid ingredients, are included in the above table, A and B, 

 where we see that in one case a slight absorption of chlo-. 

 rine, and in the other of sulphuric acid, occurred. Way, 

 however, regards these diiferences as due to the unavoid- 

 able errors of experiment, and it is certain that in Vcelck- 

 er's results similar allowance must be made. Neverthe- 

 less, these errors can hardly account for the large loss of 

 chlorine observed i:i 1 and 3, or of sulphuric acid in 2. 



Liebig found in his experiments "that a clay or lime- 

 soil, poor in organic matter, withdrew from solution of 

 silicate of potash, both silicic acid and potash, whereas 

 one rich in humus extracted the potash, but left the silicic 

 acid in solution." (Compare pp. 171-5.) 



As regards nitric acid , Knop observed in a single in- 

 stance that this body could not be wholly removed by 

 water from a soil to which it had been added in known 

 quantity. He regards it probable that it was actually 



