114 Report 8. A. A. Advancemknt of .Science. 



largely to the supply of a navigation canal to the Illinois River. The 

 permanence of the How was therefore a matter of great economic 

 importance. The forests of this region at the time of its fii-st settle' 

 ment — about sixty-three years ago — were estimated to cover at least 

 75 per cent, of the area; but marked changes have taken place, and 

 by 1903 the forest area was re^luced to 30 per cent. Since 1885 the 

 rainfall has decreased, and there are great fluctuations in the flow of 

 the river. These conditions are largely the result of forest destruction 

 and forest deterioration. The latter is a very important point, for 

 open forest growth, which not only gives access to the sun and the 

 wind, but also permits the invasion of grass and weeds, must affect 

 very unfavourably the moisture-holding capacity of the soil. Hence 

 one remedial measure would be to prevent this deterioration in the 

 remaining wood-lots and forests.* The same cause has had the same 

 effect in the State of Michigan, where about 30 per cent, of all land, 

 and over 70 per cent, of the land in the southern lialf of the state, has 

 been cleared off during the last seventy years, and mostly during the 

 last fifty. The landscape has been changed, and the rivers are subject 

 to alternate floods anfl low water. It is safe to say that by drainage 

 and the denudation of the forests in southern Michigan the subsoil 

 water lias been reduced, and the surface run-off increased, to such an 

 extent that the general welfare of the inhabitants has been affecteil. 

 The removal of the protection afforded by the forests has lesulted in 

 erosion that has destroyed thousands of acres of good land by gullying, 

 and injured thousands more by surface washing. The winds have 

 freer play, and the loss to agricultural crops from their desiccating 

 action is difficult to calculate, though the damage and the immediate 

 cause are both universally admitted. The merchant and farmer, town 

 and country, i-ailways and industries all suffer from a loss that is 

 estimated to amount to millions of dollars a year.f 



Hufher Floods and Decrease of Fermaufiit Floiv. — The cases men- 

 tioned above i-efer to desiccation resulting from the loss of forests, and 

 this is only a preliminary stage to the effect on rivers. Fires and 

 timber cutting have made serious inroads on the forests that clothed 

 the slopes of the Rocky Mountains and the head waters oi many of 

 the streams in the United States. The destruction has baied the 

 rocks by removing the vegetation, the leaves and the hunnis that for 

 centuries had been holding back the rain and snow. Where once it 

 took weeks for the water to reach the streams and rivers, it now flows 

 down in a few days or hours. This has had a very injui-ious effect on 

 the water-supply of the Unit(Ml States. Tt has iiicreased the range be- 

 tween high an<l low water, not only in the mountain states, but also 

 throughout the Mississippi valley. The result is that the mountain 

 springs and rivulets dry up far ntore rapidly, and the larger ri\ers 



* rill. Jjiiniiusliid Fhiir iif till' liorl: liii^er In, WiHConsin and Illinois and 

 Us lielat'uin to the Siinrnindinff Forests, l)y (1. F. Scliwarz, IJureau of Forestiy, 

 I'.ulletiii No. 44. 



I Suna^ Forest Injlnemes, hy Professor V. Kotli, in the .Micliigan 'J'c<-lihic. 



