350 HOW CROPS FEED. 
posable silicates. A number of analyses which illustrate 
these facts are subjoined : 
1. 2. 3. 4, 5. 6. 
, Porce- | White 
White | Red f 
Sandy Loum. | Clay. | Clay. Chay Polery 
HEIDEN. RAUTENBERG. War. 
WATER. bic. o sais ae ardieracg aia sees] 1.613 | 1.347] 6.15 6.39 | 10.36 6.18 
Organic matter.............. 2.387 | 2.003 | none | none | none | none 
Sand and insoluble silicates.| 89.754 | 88.782 | 58.08 | 80.51 | 89.46 | 58.72 
(Clay, kaolinite)............. (10.344) | (5.762) 
(BUCA ies a ccwimas < eosieee 2.630*| 4.199 | 18.73 6.80 0.04¢ | 13.41 
wm, Oxide ofiron... ..... «| 1.872 | 1.630 | 2.11 0.90 ho 14 : 
&| Aluming............... »| 1.152 | 1.288 | 12.15 4.35 : 13.90 
BU TAMIMG? sc. saieis a; iad aiadarne a 0.161 0.122 | 0.27 0.38 0.12 0.61 
Sl Maenes iB i. ca sister, oa 0.201 | 0.240} 0.29 0.17 0.08 0,43 
wed POERBR icine va sisccisionieuativei 0.242 | 0.212] 0.86 
ei BOG B is 5 wine Hone weuiyaraine 0.034} 0.141 | 1.41 . 
@,| Phosphoric acid........ 0.083 | 0.034 0.50 1.37 
& | Sulphuric acid.......... 0.007 | 0.021 ; none 5 ‘ 
” | Carbonic acid, chlorine, 
and Joss........ «2... 0.047 | 0.095 | none 
100.000 |100.006 '100.00 1100.00 |100.20 1100.00 
* This soil yiclded to solution of carbonate of soda before treatment with 
acid, 0.340 |, silica. 
+ The silica in this case is the small portion held in the acid solution, 
The first three analyses especially, show that the soils 
to which they refer, contained a silicate or silicates in 
which iron, alumina, lime, magnesia and the alkalies ex- 
isted as bascs. How much of such silicates may occur in 
any given soil is impossible to decide in the present state 
of our knowledge. In the soil, free silica, is usually, if not 
always present, as may be shown by treatment with solu- 
tion of carbonate of soda, but it appears difficult, if not 
impossible, to ascertain its quantity. Again, hydrated 
oxide of iron (according to A. Miiller and Knop) and hy- 
drated alumina* (Knop) may also exist, as can be made 
evident by digesting the soil in solution of tartrate of 
soda dnd potash (Miller, Vs. St., ZV, p. 277), or in a mix- 
ture of tartrate and oxalate of ammonia (Knop, Vs. St. 
VII, p. 41). Finally, organic acids occur to some ex- 
tent in insoluble combinations with iron, alumina, lime, 
* More probably, highly basic carbonates, or mixtures of hydrates and car 
bonates. 
