And the “ Great Carolina Marl Bed.” 47 
MINERAL MANURES. 
“There is one department,” remarks Professor Tuo- 
mey, “in which chemistry has fully redeemed its 
pledge to agriculture—the analysis of the products 
of the soil and manures. Plants analyze soils most 
accurately, and whatever of organic matters they 
contain must be found in the soil. And if we con- 
tinue to abstract these matters, by repeated cropping, 
and without making any return, sterility must be the 
result. 
“ Knowing, then, the composition of each crop, we 
know what is removed from the soil; and knowing 
also the composition of the manures within reach, we 
know what to apply. This is absolute knowledge, 
and must constitute the basis of every enlightened 
system of agriculture. , 
“ When after a succession of crops, and consequent 
abstraction of a large amount of its salts, the soil 
begins to exhibit signs of exhaustion, application is 
made to the chemist to determine what is the matter, 
or to find out if some little ingredient is not wanting 
that may be supplied without any trouble or expense. 
Supposing that this wanting ingredient be discovered, 
how is it to be procured? Lime is almost the only 
substance that we, in this country, can afford to ap- 
ply in an isolated state. The course to be pursued is 
obvious: We must study the composition of the 
failing crop, and add such manures as we know, by 
their composition, to contain the greatest number or 
quantity of the elements of the crop, trusting that 
