7 
with De Candolle in his plea for a climatic laboratory. It is evident 
that in such an institution one may reproduce to perfection the cli- 
matic conditions under which a given seed was grown, and thus 
insure a Maximum crop; or, on the other hand, by successive culti- 
vations, under successive shght changes in the artificial climate, may 
so modify the seed as to produce a new variety with a fixed habit of 
growth adapted to any natural climate that the farmer has to deal 
with. The laws of acclimatization that naturally follow from Lins- 
ser’s investigations, and, in fact, from general experience in all parts 
of the world, point to this as a most important field of future useful- 
ness. It is thus that we may hope to accelerate the natural course, 
which, on the one hand, has already produced grains adapted to the 
Russian steppes, and, on the other, will eventually evolve those 
adapted to the vicissitudes of our own arid regions and possibly our 
severe Alaskan climate. 
3. The statistical method of ascertaining the effect of a climate on 
the resulting crop consists in comparing the statistics of the sueces- 
sive annual harvests in the country at large with the statistics of the 
prevailing climatic conditions. At the close of this report I have 
given a large collection of data of this kind, sufficient, I think, to 
show that this method is very unsatisfactory because of our ignorance 
of the many details that must be considered in discussing the statis- 
tical figures. I have compiled these elaborate tables for the United 
States from the data given by the former Statistician of the Depart- 
ment of Agriculture, Mr. J. R. Dodge, and his able assistant, Mr. 
Snow, and have indicated a method of treating these figures which 
will, I think, eventually give us the best results that they are capable 
of affggding, and will be, perhaps, sufficiently accurate for the needs 
of the farmer, the merchant, and the statesman, but which can scarcely 
respond to the exact demands of agricultural physics. The great col- 
lection of data given in the reports of the Tenth and Eleventh cen- 
suses of the United States for the crop years 1879 and 1889 will, 
I hope, tempt some one to an extended study for those years. 
T shall not devote much space to the question of the relative influ- 
ence of forests and cultivated fields on the temperature and moisture 
of the local air. This has become a special study on the part of those 
devoted to forestry, and the papers of Professor Ebermayer (1873), 
Muttrich (1880), Nordlinger (1885), and others * teem with figures to 
show that in the heart of an extensive forest the mean daily varia- 
tions of temperature or the range from minimum to maximum is, on 
the average, from 2° to 5° C. less than in the open air just outside the 
forest, while a similar difference of only 1° to 2° C. exists for the 
«The full titles of the works referred to in this report will be found in section 
on “ Bibliography,” Part IV. 
