and Price of Wheat, Sfc. 
343 
the annual application of 14 tons of farmyard-manure per acre, 
for eight years in succession, and in seasons which, taken toge- 
ther, were of more than average productiveness. But if we 
adopt this as the standard produce of the plot ; then calculate 
what should be the produce in each of the subsequent twenty- 
eight years, provided it fluctuated from year to year exactly in 
the same degree as the average produce of the country at large ; 
and then take the difference between this calculated produce 
fluctuating by season alone, and that actually obtained each 
year, we ascertain the increase or decrease due to accumulation 
by manure. On this mode of calculation we get an average 
annual increase due to accumulation of 5\ bushels. If, on the 
other hand, instead of the average produce of the first eight 
years, we take the average of the whole thirty-six years of the 
application of the dung, we get, instead of 28J bushels, 32^ 
bushels, as the standard with which to compare the annual 
produce. Adopting this figure, and following the same line of 
calculation as before to exclude the influence of season, we have 
an average annual excess, due to accumulation, of only 1;^ bushel. 
There can be no doubt that, were it not for the adverse influence 
of the recent wet seasons, the estimated excess would be more 
than 5^ bushels adopting the first standard, and more than 
1^ bushel adopting the second. Probably the truth lies between 
these two figures : and, if so, it would appear that, up to the 
present time at any rate, the gradually diminishing produce on 
the unmanured plot, due to exhaustion, and the gradually in- 
creasing produce on the dunged plot, due to accumulation, 
approximately balance one another. 
The Artijicialhi-manured Plots. — Though obviously open to 
objection, in default of any better alternative, we adopt for 
these plots the average produce of the twenty-eight (or twenty- 
five) years to represent the standard yield, irrespectively of 
exhaustion or accumulation. Doing this, and excluding the 
influence of season by the same line of calculation as before, 
there is no evidence of material increase, or of material decrease, 
on either of the plots receiving ammonia-salts, other than that 
due to season. The first fourteen of the twenty-eight years 
included a number of seasons of unusually high productiveness, 
and the last fourteen a number of unusual deficiency. The 
calculations show, accordingly, an excess over the assumed 
standard produce during the first half of the period, and a closely 
corresponding deficiency over the second half, in both the cases 
where ammonia-salts were used. Where the nitrate of soda was 
employed, there was, on the other hand, a somewhat greater 
deficiency over the first period than there was an excess over 
the second, indicating for the total period a slight deficiency. 
