aneous effect, changed
their opinion, and contemned, as strongly as they had before supported,
the application of chemistry to agriculture.

That this effect should have been produced is not unnatural; for
practical men, having at that time little or no knowledge of chemistry,
were necessarily unable to estimate its true position in relation to
agriculture, and forgetting that this department of science was still in
its early youth, and burthened with all the faults and errors of youth,
they treated it as if it were already perfect in all its parts. Neither
could they distinguish between the fully demonstrated scientific truths,
and the uncertain, though probable conclusions deduced from them; and
when the latter, as occasionally happened, proved to be at variance with
practice, it is not surprising: that this should have produced a feeling
of distrust on the part of persons incapable, from an imperfect, and
still oftener from no knowledge of science, of drawing the line of
demarcation, which Liebig frequently omitted to do, between the positive
fact and the hypothetical inference, which, however probable, is, after
all, merely a suggestion requiring to be substantiated by experiment.
This omission, which the scientific reader can supply for himself,
becomes a source of serious misapprehension in a work addressed to
persons unacquainted with science, who adopt indiscriminately both the
facts and the hypotheses of the author. And this is no doubt the cause
of the vary different estimation in which the work of the Giessen
Professor was held by scientific and practical men.

Liebig's treatise was followed, in the year 1844, by the publication of
Boussingault's _Economic Rurale_, a work winch excited at the time
infinitely less interest than Liebig's, although it is really quite as
important a contribution to scientific agriculture. It is distinguished
by entering more fully into the special details of the application of
chemistry to agriculture, and contains the results of the author's
numerous searches both in the laboratory and the field. Boussingault
possesses the qualification, at present somewhat rare, of combining a
thorough knowledge of practical agriculture with extended scientific
attainments; and his investigations, which have been made with direct
reference to practice, and their results tested in the field, are the
largest and most valuable contribution to the exact data of scientific
agriculture which has yet