174 
Our Climate and our Wheat-Crops. 
As only about 5 per cent, of the total wheat-crop is derived 
from the soil itself, the remainder coming, directly or indirectly, 
from the atmosphere ; and as the amount of matter accumulated 
from either source depends mainly on the quantity, and the 
relations to one another, of heat and moisture, we cannot be 
surprised that the character of the seasons exercises such a pre- 
ponderating influence over the growth of our crops. As yet, 
however, the connection between meteorological phenomena and 
the progress of vegetation is not so clearly comprehended as to 
enable us to estimate with any accuracy the yield of a crop by 
studying the statistics of the weather during the period of its 
growth. Experience does, indeed, teach us that we mav expect 
better crops under certain conditions of the weather than under 
others. But it is only by a careful comparison of the characters 
of the seasons on the one hand, and of the quantity and quality 
of the produce on the other, for many years, that we can hope to 
acquire sufficient knowledge to enable us to assign to the various 
agencies, the sum of which constitutes the climate of the year, 
their respective values in the production of the crop. As we have 
said before (this ' Journal,' vol. ix., part 1, p. 96) : — " Thus, it 
is obvious that different seasons will differ almost infinitely at 
each succeeding period of their advance, and that, with each 
variation, the character of development of the plant will also vary, 
tending to luxuriance, or to maturation, that is, to quantity, or to 
quality, as the case may be. Hence, only a very detailed considera- 
tion of climatic statistics, taken together with careful periodic 
observations in the field, can afford a really clear perception of 
the connection between the ever-fluctuating characters of season 
and the equally fluctuating characters of growth and produce. 
It is, in fact, the distribution of the various elements making up 
the season, their mutual adaptations, and their adaptation to the 
stage of growth of the plant, which throughout influence the 
tendency to produce quantity or quality, it not unfrequently 
happens, too, that some passing conditions, not indicated by a 
summary of the meteorological registry, may affect the crop very 
strikingly ; and thus the cause will be overlooked, unless careful 
observations be also made, and the stage of progress, and tenden- 
cies of growth, of the crop itself at the time, be likewise taken into 
account." 
Still, such records as we do possess, of the conditions as to tem- 
perature and moisture of different seasons, are sufficient to account 
in great measure for the great variation in the quantity and the 
quality of our crops. The actual amount of rainfall must, how- 
ever, be carefully considered in connection with the temperature 
of the period. For example, it is obvious that a given amount 
of rain, equally distributed through the spring and summer in 
