181 
with regard to wheat in America after an extensive research, but 
within the past few years much more attention has been given to this 
subject. 
The differences between the quantities of heat required in England 
and America and the differences in the varieties of the wheat were 
apparent to Lippincott. Thus, he finds that in England the lengths of 
the periods and the sums of the temperatures were as follows: In 
1860 a period of 59 days and a sum of 3,562° F.; in 1861 a period of 
50 days and a sum of 3,225° F.; in 1862 a period of 56 days and a 
sum of 3,406° F. The reduction of the mean temperature during 
two months of 1853 by merely 2° F. cut off one-third of the crop and 
brought a famine that was already foreseen in July, 1853. On the 
other hand, it increased the exportation of wheat and flour from the 
United States from $14,000,000 in 1852 and $19,000,000 in 1853 to 
$49,000,000 in 1854. 
A careful study of the sum totals of rainfall, temperature, and sun- 
shine should enable one, in general, to foresee similar failures and 
corresponding successes in the crops of any region. 
QUETELET. 
The suggestive, but sketchy, studies of earlier writers on thermal 
constants were supplemented by more elaborate investigations and 
calculations of statistics by Quetelet (1849) in his Climate of Bel- 
gium, from his own summary (p. 62), etc., I take the following 
notes: 
The details hitherto given show sufficiently that the relative condi- 
tions of vegetation change at all times of the year in two countries 
situated at a distance from each other. Acceleration and retardation 
are quantities essentially variable, and it is erroneous to say that one 
locality has its budding period ten or twenty days sooner, for 
example, than another. This difference may be correct for one sea- 
son of the year and entirely wrong for another; and, moreover, we 
can only pretend to state a fact which apples to the majority of 
plants. 
Nevertheless the differences in the periods of budding are not so 
variable but that we can assign to them values very useful to consult 
in practice. On the other hand, science needs to establish some well- 
determined facts in order to arrive later at the knowledge of the 
laws upon which these variations depend. I believe that in the 
actual state of things I shall be able to settle upon the following 
epochs, in-order not to multiply too much the terms of comparison. 
Moreover, the numerical tables justify, to a certain extent, the dis- 
tinctions which I lay down. 
Let us first observe that the awakening of the plants is brought about 
by the cessation of the cold, and it suffices to consult the tables of 
temperatures for the different countries to determine the average 
epoch at which many plants will put out their leaves or their flowers. 
These first indications, which it is well to collect, still do not deter- 
mine, however, the general movement of vegetation which may 
