
CAPABILITIES WITH REFERENCE TO SETTLEMENT. 313 
nected with the gradual destruction of the forests over large areas, by 
fire, diminishing the rainfall. Whatever the effect may be of these de- 
structive conflagrations, in reference to the water supply of the region, 
there is no doubt that at different times almost every square mile of the 
country between Red River and the Rocky Mountains, has been sub- 
jected to them; and that hundreds of miles of forests have thus been 
converted into wide and almost treeless expanses of prairie.” Now 
that attention is so prominently drawn to the North-west as a region 
for settlement, it seems time that some legislative action, having for 
its object the prevention of these disasterous prairie fires, should be 
taken. 
736. With such a potent cause as this still in active operation, it 
would scarcely seem necessary to search further ; yet to account for 
the present treeless condition of the plains, many theories have been 
brought forward. It has been contended that the extreme fineness of 
the prairie soil prevents the growth of trees,* but in the Red River 
and Mississippi Vallies, trees are found growing, and attaining a very 
large size, on the finest varieties of this soil. Again, the peaty character 
of the soil, is urged as a cause of treelessness. It is supposed to have 
been formed during the gradual recession of great lakes, and to be 
unfavourable to the growth of trees, like that of modern peaty swamps, 
from the proportion of ulmic acid which it contains. The firm and 
tough nature of the prairie sod, and the well established supremacy 
of the grasses, is also mentioned, and is no doubt a true cause to 
a certain extent. The presence of ‘alkali’ or saline matter in the 
soil, has also been suggested as a cause, and though it may have some 
effect in exceptional localities, I have not observed that its occurrence 
in small quantity is incompatible with the growth of trees, except in 
so far as it may tend to show the too great dryness of the soil. It 
has also been stated, that as at a comparatively modern period, the 
whole interior region of America has been submerged, and as large 
lakes are known to have covered extensive areas of low-lying prairie 
in even more modern times; that the forest growth has not yet had 
time to spread again over the re-elevated surface.{ It seems to have 
been forgotten by the advocates of this last theory, that many of the 
trees best suited for growing on the prairie, have light winged and 

*Whitney, Geology of Iowa, vol. I. 
t Lesquereux, Am. Journ. Sci. and Arts, May, 1865. Geology of Illinois, vol. 1., 1866, &c. 
} A. Winchell, Am. Journ. Sci. and Arts, Nov., 1864. Sketches of Creation, 1874. 
\ 
