Price of Wheat , over 40 Harvest-Years, 1852-3 to 1891-2. 87 
Adopting 16 bushels as the standard, the result is, that 
with an average actual produce over the twenty-eight years of 
rather over 12^ bushels, the average decline is less than 34 
instead of nearly 44 bushels when 1 7 was taken as the standard ; 
and the rate of decline from year to year is rather less than one- 
quarter of a bushel, instead of, as before, nearly one-third of a 
bushel. And, whilst with a standard of 17 bushels the calcu- 
lated produce in the twenty-eighth year was little more than 8 
bushels, with a standard of 16 bushels it is more than 9 bushels. 
Then, the results for forty years show, with a standard of 16 
bushels, and an actual average produce of about 124 bushels, an 
average decline of about 3^, instead of about 4^- bushels with a 
standard of 1 7 bushels ; and the average rate of reduction from 
year to year is little more than one-sixth of a bushel instead of 
nearly one-quarter of a bushel, with 17 bushels as the standard. 
Further, whilst with 17 bushels as the standard, the calculated 
produce would amount to little more than 8 bushels in the 
fortieth year, showing a deficiency of nearly 9 bushels, with a 
standard of 16 bushels the calculated produce would be more 
than 9 bushels in the last year, and the reduction less than 7 
bushels since the beginning. 
Upon the whole, therefore, assuming the standard produce 
of the unmanured plot to have been 16 bushels per acre inde- 
pendently of material exhaustion, there was an average decline 
from year to year of rather less than a quarter of a bushel over 
the twenty-eight years, and of little more than one-sixth of a 
bushel over the forty years. It will be seen that a return of 
better seasons since the first twenty-eight has led to a consider- 
able reduction in the estimate of the rate of decline from year to 
year due to exhaustion. It remains to be seen what will be the 
result in the future ; and whether a point has already been, or 
will in time be reached, at which the produce will remain 
constant, excepting so far as it is influenced by the fluctuations 
of the seasons. 
The Farmyard Manure Plot. — It has been seen that the un- 
manured plot has declined in yield and fertility 7- ; but there can 
be no doubt that the farmyard manure plot has, on the other 
hand, increased in fertility. Analyses of the surface soil at 
different periods has shown that it has become about twice 
as rich in nitrogen as that of the unmanured plot. It has, 
indeed, been shown on several occasions, that a large amount of 
the constituents of farmyard manure accumulates within the 
soil, and that they are very slowly taken up by crops ; in fact, 
notwithstanding this great accumulation within the soil, the 
wheat crops on the dunged plot seldom, if ever, show over 
