Relation of Climate to Vegetation 123 
further reduce the local temperature, brings the air below 
the actual point of saturation and rain falls. It is therefore 
to be noted that forests affect precipitation in the form of 
rain or snow, to the extent that rains become more frequent 
in forest regions than elsewhere. This effect. then, is of a 
local nature, but has popularly been interpreted to mean 
that forests increase the total rainfall, which can hardly be 
regarded as true, since they do not increase the absolute 
amount of water in the atmosphere, but only the relative 
quantity. And, moreover, the weight of scientific evidence 
thus far available, shows that such influence is not pro- 
duced. One of the most conclusive arguments bearing upon 
this point, is that of Mr. Henry Gannett in a recent number 
of Science. For this purpose he employs large areas in the 
‘United States where, since colonial times, deforestation and 
reforestation have been going on on a very large scale. The 
deforesting of 25,000 square miles in New England, prior to 
1860, was found to be attended by an actual increase in 
annual rainfall. The deforesting of 40,000 square miles in 
Ohio was attended by an almost inappreciable diminution 
in rainfall, while the reforesting of 100,000 square miles of' 
prairie in Iowa, Missouri, Minnesota and Illinois has been 
accompanied by a slight diminution. And Mr. Gannett’s 
conclusion that it is useless “to discuss further the influ- 
ence of forests upon rainfall from an economic point of 
view,” is to be endorsed as essentially correct. 
But the question is then pertinent, How do we account 
for the shrinkage of streams, the drying of springs and 
other changes which are known to attend the removal of 
forests? Southern Kurope and some parts of Asia Minor 
have, by removal of their once abundant forests, become 
converted into dry wastes. ‘The question here raised is of 
the greatest importance, and each year demands more seri- 
ous consideration. In their report for 1885, the Forestry 
Commission for the State of New York, the chairman of 
which is no less an authority than Prof. C. 5. Sargent, of 
Harvard University, give expression to the following 
views, based upon observed facts:—“The most important 
