432 AGRICULTURAL REPORT. 
forces of nature, with heat, light, electricity, and with energy generally—with that form 
of it called vital force—and thus regulates the rate and mode of growth m a manner 
wholly unknown to mere chemical food elements. Thus, humus retains the moisture 
in a soil; by its slow decomposition it evolves heat, and raises the temperature above 
that of land not supplied with it. Thus heat and moisture are gradually offered to the 
growing vegetable germs. By its darker color it absorbs the solar heat, which is for a 
time retained, and is therefore converted into energy or vital power by the presence of 
humus. <A gentle development of carbonic acid takes place, which, dissolved and 
retained by the moist humus, dissolves phosphate and carbonate of lime, and renders 
even alkaline soils more readily soluble. And further, this carbonic acid decomposes 
the double and trisilicates in the soil, liberating the silica in a finely-divided and solu- 
ble form suitable for the growth of cereats. 
This isa long list of properties dependent upon the presence of humus 
in the soil, which are too much overlooked by the upbolders of the 
mineral-manure theory. 
When we acknowledge that to Liebig belongs the idea of employing 
mineral agents to increase the fertility of soils, it must not be forgotten 
that marling lands, or applications of lime carbonate, is not new, and was 
practiced long before the birth of that illustrious chemist. Plaster or 
gypsum was similarly applied by our own Franklin and others the lat- 
ter half of the last century. So also the use of common salt, bone-dust, 
and even guano, is little else than illustrations of the practice of supply- 
ing mineral principles to the soil. These were applied from some vague 
knowledge that the land was somehow benefited by their action; but 
the idea of a mineral food for plants—the “ mineral theory” as it is 
termed—and its application to practice dates no farther back than 1839, 
and justly belongs to Liebig; yet the first essays in this direction were 
little else than failures. lLiebig believed that rain-water carried off 
much of soluble saline matter from the land, or sweeps it down into the 
sub-soil out of the reach of any but the deepest-rooted plants. He 
thought also that, as cereals require alkalies and silica, it would be best 
to supply these after they had been fused together, as occurs in glass- 
factories, so that they might very slowly decompose, and keep up a 
gradual but moderate supply of the necessary mineral food. He alludes 
in the chapter on soils in his Agricultural Chemistry (1840) to the ash of 
straw from the bake-ovens of Hesse, and to the use of soluble glass as 
a mode of giving both alkalies and silica to plants. He writes: 
A compost manure, which is adapted to farnish all the inorganic matters to wheat, 
oats, and barley, may be made by mixing equal parts of bone-dust, and a solution of 
silicate of potash, (known as soluble glass of commerce,) allowing this mixture to dry, 
and then adding ten or twelve parts of gypsum, with sixteen parts of common salt. 
Such a compost would render unnecessary the animal manures, which act by their in- 
organic ingredients. 
Here is the idea of replacement of organic by mineral manures, whieh 
lies at the bottom of the system of modern manuring. 
Liebig’s fear of exhaustion of soils by rain-water or drainage carrying 
off soluble saline matter proved to be groundless ; for Way showed that 
arable land, by virtue of the clay which it contains, possesses a remark- 
able absorbing power, rendering it capable of appropriating and fixing 
within its particles the important saline matters and nitrated compound 
suitable for vegetable growth, presented to that clay by the water hold- 
ing them in solution. Liebig’s fear of lixiviation of the soil was ground- 
less, and a growing appreciation of this cireumstance—the absorbent and 
retentive power of saline matter by the clay in a soil—led Kuhlmann, 
Boussingault, Gilbert and Lawes, Voelcker, and above all, Georges 
Ville, to adopt with marked success the employment of various saline 
matters as substitutes for farm-yard manure as a fertilizing agent. 
Hence to the idea of “mineral theory” is now superadded that of 
“chemical manures.” It is, however, to the exertions of Ville that the 
