1884.] 
Analyses of Boohs. 
2 §7 
Geology of Wisconsin. Survey of 1873-79. Vol. IV., accom- 
panied by an Atlas of Maps. Published under the direction 
of the Chief Geologist by the Commissioners of Public 
Printing. 1882. 
This volume deals with the Upper Mississippi region, the Lower 
St. Croix region, the ore deposits of South-western Wisconsin, 
the quartzite of Barron and Chippewa counties, the Flambeau 
region, the crystalline rocks of the Wisconsin Valley, the super- 
ficial geology of the Upper Wisconsin Valley, and expounds, 
lastly, the character and methods of the geodetic survey. 
It is especially to be noted to what an extent the evils resulting 
from the reckless destruction of forests have forced themselves 
upon the notice, not merely of scientific theorists, but of far- 
sighted practical men throughout America. We know that not a 
few authorities are of opinion that all the water of our globe will 
be ultimately absorbed into its interior, leaving the surface arid. 
To prevent, or at least retard, this process is within the power of 
man if he will only use the knowledge which he possesses. But 
if in that greed which is the dominant feature of modern life he 
“ clears ” the country the result is, locally, the conversion of 
fertile land into a desert, and, generally, an impulse given to the 
desiccation of the earth. 
As regards the quantity of moisture pumped up from the earth 
bo trees and restored to the atmosphere, Dr. J. M. Anders has 
made some very interesting determinations. He finds that the 
average evaporation from soft thin-leaved plants in clear weather 
is about i£ ozs. troy for every square foot of surface per day of 
12 hours. Hence a single elm, of no very large size, would throw 
off 7 £ tons of watery vapour in twelve hours, and a grove of 
1000 trees, oaks, maples, &c., would exhale over 45,000 “ bariels 
of water during every clear day of its season of growth. It is 
too much to assume that, without the agency of the trees, this 
water would all have been restored to the surface by the agency 
of springs. The author notes that there has been an evident 
increase of rainfall over certain areas on the plains of Colorado 
which have been irrigated for five or six years and planted with 
trees, &c. It seems to him that vegetation has contributed to 
this result bv pumping up the water running beneath the suiface. 
The roots of many trees penetrate the ground to the depth of 
twenty feet and more. . . . 
It is asserted by some that throughout the prairie region 01 
America the annual rainfall is, in three years out of five, suffi- 
cient for the purposes of the farmer. 1 he author contends, 
however, that in the denuded regions vegetation would be im- 
proved if the rainfall were more distributed, so as to render the 
heavy rains lighter and light showers more frequent. In Europe, 
he adds floods are known to be more numerous, and in Asia 
droughts more frequent, since vast forests have been destroyed. 
VOL. VI. (third series) x 
