494 
Agricultural Chemistry. 
with clear reference to the amount of the various mineral con- 
stituents removed from the land in the different crops. Was there 
not, however, we may ask, in the very facts here recorded, namely, 
that notwithstanding the exhaustion of minerals the clover was 
still so good a preparative for wheat — was there not in these 
coincident facts, that which would rather lead us to suppose, that 
the henefits arising from the order of succession merely of re- 
storative and other crops, was little dependent on the mineral 
requirements of the individual crops ? — and in fact, that if only 
the restorative crop, with its large demand for minerals, were 
enabled to grow luxuriantly, we might then conclude, that the 
soil was so rich in available mineral constituents, that the suc- 
ceeding crop with its comparatively meagre demand, and to 
which the former is known to be so subservient by the matters 
it leaves behind it, was little likely to find them wanting ? 
Baron Liebig, however, carries tlie mineral explanation of ro- 
tation very much further, when he says, in regard to M. Boussin- 
gault's opinions : — 
" But all these conclusions are thoroughly erroneous ;/or, if they were not so, 
it must follow that potass, lime, and silica ^jlants, unless they helonged to the 
Icguriiinosw, would not produce any nitrogen, unless they were siapplied with 
manure containing that element." — A.th Edition, j). 208. 
Nor could Baron Liebig have reasoned as he did in regard to 
the analysis of M. Boussingault's rotations, had he, not only 
dwelt more upon the composition of each individual crop and 
their relations to each other, but at the same time recognised 
that which he will not even now admit, namely, that any in- 
creased produce of wheat is obtained only at the cost of more 
nitrogen provided in the manure than is recovered in that in- 
creased produce. 
But let us see how the mineral tlieorij mf rotation, as expressed 
in Baron Liebig's 35th Proposition, is consistent with the evi- 
dence of direct experiment. 
In Table VIII. we have the chemical statistics of three actual 
rotations ; in each of which the course consisted of Swedish 
turnips, barley, clover, and wheat ; and in all cases the entire 
produce of the swedes (both leaf and bulb) was removed from 
the land. 
In rotation 1, the course commenced without any manure at all. 
In rotation 2, it commenced with a manure of superphosphate 
of lime alone. 
And in rotation 3, with a liberal mixed manure, containing 
rape-cake, ammonia-salts, potash, soda, and magnesia, and 
superphosphate of lime. 
Tlie constituents per acre which are calculated are, dry organic 
matter, nitrogen, total mineral matter, and the phosphoric acid. 
