of free atmospheric nitrogen. His first contribution to the
subject was published in 1838, but can scarcely be regarded as
possessing much scientific value, except in so far as it stimulated
further research. Some thirteen years later he returned to this
question; and during the years 1851-1855 carried out most elaborate
experiments, the results of which, until quite recently, were generally
regarded as having, along with the experiments of Messrs Lawes, Gilbert,
and Pugh, definitely settled the question.[12]

In 1839 Boussingault was elected a member of the French Institute, an
honour paid to him in recognition of his great services to agricultural
chemistry.[13]

The foregoing is a brief epitome of the history of the development of
agricultural chemistry up to the year 1840, the year which witnessed the
publication of one of the most memorable works on the subject, which has
appeared during the present century--Liebig's first report to the
British Association, a work which may be described as constituting an
epoch in the history of the science. Liebig's position as an
agricultural chemist was so prominent, and his influence as a teacher so
potent, that a few biographical facts may not be out of place before
entering upon an estimate of his work.

_Liebig._

Liebig was born at Darmstadt in the year 1803. He was the son of a
drysalter, and early devoted himself to the study of chemistry in the
only way at first at his disposal--viz., in an apothecary's shop. Soon
finding, however, his opportunities of study limited, he left the
apothecary's shop for the University of Bonn. He did not remain long at
Bonn, but in a short time left that university for Erlangen, where he
studied for some years, taking his Ph.D. degree in 1822. His subsequent
studies were carried on at Paris under Gay-Lussac, Thenard, Dulong, and
other distinguished chemists. Through the influence of A. Humboldt, who
was at that time in Paris, and whose acquaintance he was fortunate
enough to make, he was received into Gay-Lussac's private laboratory.
In 1824--that is, when he was only twenty-one years of age--he was
appointed Professor _Extraordinarius_ of Chemistry at the University of
Giessen. Two years later he was appointed to the post of Professor
_Ordinarius_--an appointment which he held for twenty-five years. In
1845 he was created Baron, and in 1852 appointed Professor at Munich. He
died in 1873.

_His First Report to British Association.