232 
GEOLOGY OF THE THIRD DISTRICT. 
rock exists, and the soil is its product: Why different native growths, not far distant from 
each other, differ where no cause is apparent, unless from difference in the soil, and this not 
apparent to the senses ? Why land which formerly yielded wheat abundantly, ceases to pro¬ 
duce healthy wheat, and that but in small quantity ? A question which could be answered by 
the analysis of such soil, and the same in a hedge row or elsewhere near by, where the wheat 
could not be sown. Were the subject pursued in some such manner, the utility of the analysis 
of soils would doubtless soon be apparent; but continued in the old or present mode, the good 
received would be of little moment. 
The greatest benefit, I should suppose, which is to await the agriculturist, is from rotation ; 
all other methods being secondary to it. It is the great law which geology makes known, and 
thereby confirms the first chapter of Genesis, which asserts a succession. One thing prepares 
the way for another, and an order of succession has been established from the beginning. The 
kind of plants which the farmer ought to grow, and their order of precedence, should be one 
of his first lessons. Next to rotation would be mixtures of different earthy materials, especially 
those of opposite quality from the soil to be improved, which probably may be one of the 
causes why change becomes necessary ; and hence a shorter rotation might advantageously 
be pursued, for the great benefit of this operation may arise from the change which plants 
produce in soil by excretion, decay of materials, and mechanical action. 
From the great body of well informed practical agriculturists now engaged in improving 
their soil by earthy mixtures of various kinds, manures, saline materials, and rotation, it is 
hoped that agriculture, a subject so obscure and yet of such vital importance, will, by the 
conjoined aid of theorists versed in its practice, take its rank among the exact sciences; and 
as it is the basis of civilization, it will in practice be considered among the most ennobling of 
human pursuits, and become consequently the prime element of education. 
Certain earthy mixtures which contain no nutriment, such as the marl of New-Jersey, 
possess a highly fertilizing quality, the efficient cause of which is as yet unknown; for it can 
not be the potash contained therein, as was formerly supposed, since in that case micaceous 
or primary soils would be more productive than they are. Too little attention it seems to 
me, has hitherto been given to the effects developed by the action of the sun’s rays on diffe¬ 
rent colored particles in the soil: the whiter particles producing reflection in excess, may give 
rise to a repellent force; while the darker colored ones, being less reflective, receive the full 
influence of the calorific rays, and thereby evolve the elective affinity, or force of combination. 
By the assiduous study of the laws of these two forces, which have a close analogy with the 
powers of life, we would probably do more to remove the difficulty in question, than by fol¬ 
lowing any course which has been hitherto pursued. 
No fact is more obvious than the connection generally between rock and soil, and soil and 
population. Where all things else are the same, the number of inhabitants in all countries 
where man cultivates the earth, and is unfettered, are in direct proportion to the goodness of 
the soil. This is exemplified in every part of the district. The best soils are those of the 
