362 HOW CROPS FEED. 
the soil must contain the ash-ingredients of plants, together 
with assimilable nitrogen-compounds in proper quautity 
ead proportion. The composition of a very fertile soil is 
well exhibited by Baumhauer’s analysis of an alluvial de- 
posit from the waters of the Rhine, near the Zuider Zee, 
in Holland. This soil, which produces large crops, con- 
tained— 
Surface. 15 inches deep. 30 inches deep. 
Insoluble silica, quartz, 57.646 51.706 55.372 
Soluble silica, 2.340 2.496 2.286 
Alumina, 1.830 2.900 2.888 
Peroxide of iron, 9.039 10.305 11.864 
Protoxide of iron, 0.350 0.563 0.200 
Oxide of manganese, 0.288 0.354 0.284 
Lime, 4.092 5.096 2.480 
Magnesia, 0.130 0.140 0.128 
Potash, 1.026 1.430 1.521 
Soda, 1.972 2.069 1.937 
Ammonia,* 0.060 0.078 0.0%5 
Phosphoric acid, 0.466 0.324 0.478 
Sulphuric acid, 0.896 1.104 0.576 
Carbonic acid, 6.085 6.940 4.705 
Chlorine, 1.240 1.302 1.418 
Humic acid, 2.798 3.991 3.428 
Crenic acid, 0.771 0.731 0.037 * 
Apocrenic acid, 0.107 0.160 0.152 
Other organic matters, and com- 
bined water (nitrates ?), 8.324 7.700 9.348 
Loss in analysis, 0.540 0.611 0.753 
100.000 100.000 100.000 
A glance at the above analyses shows the unusual rich- 
ness of this soil in all the elements of plant-food, with ex- 
ception of nitrates, which were not separately determined. 
The alkalies, phosphoric acid, and sulphuric acid, were 
present in large proportion. The absolute quantities of 
the most important substances existing in an acre of this 
soil taken to the depth of one foot, and assuming this 
* The figures are probably too high for ammonia, because, at the time the analy- 
Bes were made. the methods of estimating this substance in the soil had not been 
studied sufficiently. and the ammonia obtained was doubtless derived in great 
part from the decomposition of humus under the action of an alkali, 
