142 AGRICULTURAL REPORT. 
braces that of absorbing the moisture and the oxygen of the air with 
rapidity, &c. 
We have already stated that the physical properties of arable soils, 
and the physical influences of the atmosphere, have a greater direct 
action upon vegetation than those properties and influences purely 
chemical, because the first are anterior to and serve as a basis for the 
last. We proceed to corroborate this announcement by the learned 
opinion of the celebrated chemist and agriculturist, Boussingault, which 
‘proves how far this question is still in its infancy. He says: 
At an epoch which is not yet very distant, it was believed that a close connection 
existed between the composition and the quality of arable soil. Numerous analyses 
soon modified this opinion by demonstrating that the mineral elements have not 
always the importance which is attributed to them. Schiibler tried even to prove 
that the fertility of a soil depends a great deal more upon its physical properties, its 
aggregate condition, its aptitude for imbibition, &c., than on its chemical constitution. 
That which characterizes cultivable soil, whose base consists of disaggregated mineral 
substances, is the presence of organic remains more or less modified, such as humus and 
compost. Vegetable earth, properly called, results from this association. In regard to 
its intimate nature, we fear not to affirm that, in spite of its apparent simplicity, we 
have still a very imperfect knowledge of it. This absorbing faculty, as mysterious aq 
unexpected, which the soil exercises on ammonia, lime, potash, and the salts of different 
bases, discovered by Thompson and Way, is a palpable proof of it. The chemical 
composition and the physical properties do not admit of pronouncing upon the degree 
of fertility of earth. Direct observation is necessary. It is imperative to cultivate a 
plant in the soil, and ascertain its vigor and development. The analysis will be useful 
in determining the quantity and quality of assimilating elements.* 
The memoir of Schiibler comprises one hundred pages. I have made 
an abstract of the principal parts which may interest farmers, excluding 
all the tables of the physical properties of different soils. I may add 
that the experiments of Schiibler are unique up to the present time, and. 
still preserve their scientific value on that account. 
Weight of the soil_—In determining this, a particular distinction is to 
_ be made between the peculiar specific gravity of the several portions 
of earth, and the absolute weight of a determinate volume, as of a cubie 
inch or foot of the several soils. 
1. Sand, either in its wet or dry state, is the heaviest part of arable 
soil, certain fine slaty marls approaching the nearest to sand in this re- 
spect. 
2. Oalcareous and siliceous sands differ but little in this point, calea- 
reous sand being, however, the heaviest of the common constituents of 
arable soil. 
3. The clays are lighter the more clay and the less sand they contain. 
4, Lime exhibits great difference in weight, according to its fineness 
and mode of preparation. In slaked lime the weight is remarkably less, 
even after it has been resaturated with carbonicacid. The explanation 
of this seems to be the great expansion of quicklime on its combination 
with water. Dolomite sand, or a combination of lime and carbonate 
of magnesia, is much heavier than either of its component parts in a 
separate state. Its specific gravity rises to 2.82 and 2.83, and even mag- 
nesian stony marls often possess this greater weight. 
5. The carbonates of magnesia, obtained by precipitation from solu- 
tions, are the least weighty of the usual ingredients of soil. In arable 
soils magnesia 1s usually found in combination with lime or silica, where 
its form is coarser, and its physical properties resemble more closely 
those of sand. 
6. Humus has the least spesific gravity, and, excepting pure artificial 
magnesia, the least absolute weight. 
* Annales des Sciences Naturelles, 1859, vol. xii, p. 354. 
* 
