h carbonic acid more than pure water which has been
boiled. The experiments of Prof. Rogers of the University of
Virginia, as published in Silliman's Journal, have a direct bearing
on this subject. The researches of Prof. Emmons of Albany, in his
elaborate and valuable work on "Agriculture," as a part of the
Natural History of New York, show that 10,000 parts of soil yield
only from one to three parts of soluble silica. The analyses of Dr
Jackson, as published in his Geological Survey of New Hampshire,
give similar results. Earth taken from an old and badly exhausted
field in Georgia, gave the writer only one part of soluble flint in
100,000.

What elements of crops rain water, at summer heat, will dissolve out
of ten or twenty pounds of soil, in the course of three months, is a
point in agricultural science which should be made the subject of
numerous and rigid experiments. In this way, the capabilities of
different soils and their adaptation to different crops may be
tested, in connection with practical experiments in field culture,
on the same kind of earth.

Few wheat-growers are aware how much dissolved flint an acre of good
wheat demands to prevent its having coarse, soft, and spongy stems,
which are anything but a healthy organization of the plant. In the
Journal of the Royal Agricultural Society of England, vol. 7, there
is an extended "Report on the Analysis of the Ashes of Plants, by
Thomas Way, Professor of Chemistry at the Royal Agricultural
College, Cirencester," which gives the result of sixty-two analyses
of the ash of wheat, from as many samples of that grain, mostly
grown on different soils and under different circumstances.

In this report are given the quantity of wheat per acre, the weight
of straw cut close to the ground to the acre, and also that of the
chaff. These researches show, that from ninety-three to one hundred
and fifty pounds of soluble flint are required to form an acre of
wheat; and I will add from my own investigations, that three-fourths
of this silica is demanded by nature during the last sixty days
preceding the maturing of the crop. This is the period in which the
stem acquires its solidity and strength, and most of its
incombustible earthy matter. The quantity of this varies from three
to fifteen per cent. of the weight of the straw. Pr