The great use of the soil is to afford support to 
the plant, to enable it to fix its roots, and to derive 
nourishment by its tubes slowly and gradually, 
from the soluble and dissolved substances mixed 
with the earths. 
That a particular mixture of the earths is con- 
nected with fertility, cannot be doubted : and al- 
most all sterile soils are capable of being improved, 
by a modification of their earthy constituent parts. 
I shall describe the simplest method as yet dis- 
covered of analysing soils, and of ascertaining the 
constitution and chemical ingredients which appear 
to be connected with fertility ; and on this subject 
many of the former difficulties of investigation 
will be found to be removed by recent enquiries. 
The necessity of water to vegetation, and the 
luxuriancy of the growth of plants connected with 
the presence of moisture in the southern countries 
of the old continent, led to the opinion so prevalent 
in the early schools of philosophy, that water was 
the great productive element, the substance from 
which all things were capable of being composed, 
and into which they were finally resolved. The 
“ olqhttw i vlbu uocoq ” of the poet, “ water is the 
noblest,” seems to have been an expression of this 
opinion, adopted by the Greeks from the Egyp- 
tians, taught by Thales, and revived by the alche- 
mists in late times. Van Helmont, in 1610, con- 
ceived that he had proved, by a decisive experi- 
ment, that all the products of vegetables were ca- 
pable of being generated from water. His results 
were shewn to be fallacious by Woodward in 1691 ; 
but the true use of water in vegetation was tin- 
