periments of serious value.
Indeed it may be safely affirmed, in the light of subsequent
experiments, that it was impossible for this question to be decided at
this early period, from the fact that analytical apparatus, of a
sufficiently delicate nature, was then wholly unknown. Indeed it is only
within the last few years that it has been possible to carry out
experiments which may be regarded as at all crucial. A short sketch of
the development of our knowledge of the relation of nitrogen to the
plant will be given further on.

_Sir Humphry Davy's Lectures._

A series of lectures on agricultural chemistry, delivered by Sir Humphry
Davy during the years 1802-1812, for the Board of Agriculture, and
subsequently published in book form in the year 1813,[9] affords us an
opportunity of gauging, pretty accurately, the state of knowledge on the
subject at the time.

_Position of Agricultural Chemistry at beginning of Century._

In his opening lecture Davy says: "Agricultural chemistry has not yet
received a regular and systematic form. It has been pursued by competent
experimenters for a short time only. The doctrines have not as yet been
collected into any elementary treatise, ... and," he adds, "I am sure
you will receive with indulgence the first attempt made in this country
to illustrate it by a series of experimental demonstrations."

He further on remarks: "It is evident that the study of agricultural
chemistry ought to be commenced by some general inquiries into the
composition and nature of material bodies, and the law of their changes.
The surface of the earth, the atmosphere, and the water deposited from
it, must either together, or separately, afford all the principles
concerned in vegetation, and it is only by examining the chemical
nature of these principles that we are capable of discovering what is
the food of plants, and the manner in which this food is supplied and
prepared for their nourishment."

Davy goes on further to say: "No general principles can be laid down
respecting the comparative merits of the different systems of
cultivation and the various systems of crops adopted in different
districts, unless the chemical nature of the soil, and the physical
circumstances to which it is exposed, are fully known."

He recognises the enormous importance of experiments. "Nothing is more
wanting in agriculture than experiments, in which all the circumstances
are minutely and scientifically detailed."