A(jricidtural Cliemistry. 
439 
experiment up to the present time — that is to say, from 1844 to 
1855 inclusive. And, as before, we give in this place as little 
detail as possible, in order that the main and more general facts 
may stand out the more prominently. 
The plan of the diagram is as follows : — 
Tn the top line of figures, are stated the years during which 
the experiments were conducted. In the second line of figures 
the total produce (corn and straw) per acre per annum of Plot 3 ; 
the continuously unmanured plot. 
In the third line of figures, we have the produce of Plot 10a ; 
which was manured in the first year with a mineral mixture, con- 
taining superphosphate of lime and silicate of potass, and in 
every succeeding year, with a somewhat excessive amount of 
ammonia salts only. 
In the fourth line of figures, is given the total produce of Plot 
\0b ; which in the first year had the same minerals as Plot lOa, 
and afterwards, sometimes the same amount of ammonia salts as 
^the latter, sometimes no manure at all, sometimes a complete 
mineral manure in addition to the ammoniacal salts, and some- 
times the mineral manure alone. 
And, in the two lower lines of the diagram, we have the increase 
of total produce over that of the unmanured plot, on the Plots 10a 
and lOi respectively. 
And in order that the comparison, both as to the general cha- 
racter of the manuring, and the amount of produce, on the several 
plots, may be brought to one convenient view, the statement of 
the manuring is not repeated ; but only indicated by squares of 
shading, which may be supposed to represent the different plots, 
thus : — 
Unmanured — unshaded. 
Mineral manure — horizontal shading. 
Ammonia salts — perpendicular shading. 
Minerals and ammonia salts together — dotted shadiiig. 
Before entering upon a comparison of the results of the several 
plots, we must pass under review Baron Liebig's remarks on the 
produce of the unmanured plot ; by which he not only seeks to 
show, that our soil was naturally so rich in available mineral con- 
stituents, as to be utterly unfit for experiment — an objection of 
which we have already disposed — but he also seeks to draw the 
conclusion, from the variable amount of produce of the unma- 
nured plot in different years, that this was due to the variable 
amount of mineral constituents dissolved in the soil in the same 
time ; and hence, he seeks to claim the greater accumulation by 
the plant in one year than in another of carbon and nitrogen 
trom atmospheric sources, simply as the result of an increased 
supply to the plant of soluble or available minerals. 
