458 
Agricultural Chcmistrij. 
pliate of liinc, gave nearly equal amounts of produce ; tliougli 
plot 22f having rather the most of the manui'e, gave also rather a 
higher average produce. 
In 1846, the now unmanured plot 7 (which, however, had 
received a large quantity of powdered apatite two years pre- 
viously) yielded next to nothing; plot 21, now unmanured, but 
having a larger residue of phosphate of lime in the soil, and in 
a more easily soluble form than plot 7, gave 1 J tons of bulb ; and 
plot 22, with its large residue of phosphate of lime, as well as 
annual additional supply of superphosphate of lime, gave nearly 
2 tons. 
In 1847, plot 7 gave rather more than 2i tons ; plot 21, with 
its residue of phosphate of lime, gave nearly 4 tons; and plot 
22, with its additional supph/ of superphosphate, as well as resi- 
due, gave rather more than 5^ tons. 
In 1848, the comparatively non-residue plot (7) gave 1 ton of 
turnips ; the residue-plot, (3> tons ; and the residue, with addi- 
tional supply, more than 10^ tons. 
In like manner, to the end of tlie experiment, it is seen that 
the residue-plot 21 always gives a considerable increase (vary- 
ing according to season) over the comparatively non-residue plot 
7 ; and again, plot 22, with both its accumulating residue and its 
additional supply, in every case gives a considerable increase over 
the residue-plot 21, although the latter, even up to the last year 
of the experiment, still retained a large proportion of the pre- 
viously added phosphate, besides all that must have been avail- 
able, during the ten years, from the stores of the soil itself. 
Now it is quite certain, that on plot 7 there was much more 
phosphate supplied in the apatite in 1844, and derivable from 
the annually available stores of the soil, than was necessary to 
supply with phosphoric acid a much larger produce than was 
obtained on that plot. It is also quite certain, that the much 
larger produce on plot 21 than on plot 7 must have been due to 
the residue of the manuring of the years 1 843-4-5. If any one, 
therefore, were to assert that, under the circumstances of this 
plot 21, "it was the free sulphuric acid which produced the 
result," it would certainly not " be difficult to disprove the asser- 
tion." And again, it is certainly also true, that the further in- 
crease obtained on plot 22 over plot 21 must be due to the 
additional mixture of phosphate of lime, mixed with sulphuric 
acid, which was annually supplied to it. And, as we have seen 
that on plot 21, a supply of phosphate far in excess of that con- 
tained in the crop produced — the action of which could 7iot be 
attributed to free sidphuric acid — did give an increase, and as we 
well know that any free sulphuric acid which might reach the 
soil would in a very short time be neutralized, the reader will 
