Price of Wheat, over 40 Harvest-Years, 1852-3 to 1891-2. 89 
average increase of only about 3f instead of about 5 bushels over 
the twenty-eight years, and of only 5^- bushels instead of 
over the forty years ; whilst the average increase from year to 
year, if uniform throughout the period, would be little more 
than one-quarter of a bushel instead of nearly § of a bushel over 
the twenty-eight years, and little over one-quarter of a bushel 
instead of nearly one-third of a bushel over the forty years. 
The general result is, then, that if we exclude the produce of 
the first of the eight preceding years (1844), which the fact of 
the high produce over the country at large, and the low produce 
of the experimental plot, seems fully to justify, we get a stan- 
dard produce of the farmyard manure plot of 29 3 instead of 
28£ bushels by which to calculate the subsequent increase from 
accumulation ; and the estimated rate of increase is accordingly 
lower. 
The Artificially-manured Plots. — Neither the previous history 
of the plots, nor common experience, enables us to adopt a 
standard average produce for the respective manures, with which 
to compare the actual produce each year, so as to form a judg- 
ment whether there has been progressive decline or progressive 
increase in the productive effect of the manures irrespectively 
of fluctuations dependent on season. If we take the average 
produce of either of the plots over the twenty-eight or the forty 
years as its standard produce, and then take the difference 
between this standard and the actual yield each year, we get 
more or less difference, sometimes plus and sometimes minus in 
the individual years, according to the characters of the season ; 
but over the total period of twenty-eight or forty years, the 
average of which is taken for the standard, the pluses and the 
minuses necessarily balance one another ; showing, therefore, 
neither progressive decline nor progressive increase due to the 
manure. 
A careful study of the results in detail also indicates that there 
is practically no appreciable variation from year to year in the pro- 
duce of the respective manures, other tliair that obviously attri- 
butable to the seasons. Or, if we divide the total period into a 
number of shorter ones, the difference of result for each of the 
shorter periods is again seen to depend on the favourable or un- 
favourable conditions of the seasons included. On the other 
hand, the examination clearly shows, that the selected artificially 
manured plots give a proportionally higher produce in seasons 
of high productiveness than the excess over the average in the 
country at large would indicate. In other words, so far as the 
yields of the selected artificially manured plots are brought 
into the estimates, they tend to indicate somewhat too high a 
