148 PRACTICAL ARBORICULTURE 



sive. This condition can be changed by the systematic planting of trees in 

 belts to break the continuity of the currents and prevent such an accumula- 

 tion of heat by the surface currents. At each successive obstruction the 

 whirls or counter currents would mingle the cold air of the upper strata with 

 the hot surface current, equalizing the temperature by reducing the heat at 

 the surface. 



In all the region traversed by these siroccos, as well as the entire prairie 

 country, the scant timber lies in the low valleys, the high rolling prairies 

 having no wood, while the trees in the valley are all below the average surface. 

 Were this reversed, and the trees placed upon the highest lands, the effect 

 would be very different from what it now is, as the cold and hot currents 

 would be equalized by the obstructions. 



Opponents will say that hot air always rises directly and does not pass 

 horizontally along the surface. 



But water traverses a thousand miles of underground strata, enters the 

 porous sandstone at the Great Falls of the Missouri and reappears in the 

 valley of the James, in Dakota, rising two hundred feet above the surface. 

 Years of actual experiences, with the facts before us, it is self-evident that 

 this hot surface current does traverse the region named each season, and 

 these truths are well known to every resident of the territory described. The 

 pressure of the overlying atmosphere, which is colder than the sirocco, so 

 long as there are no mountains, forests or obstruction to divert the sirocco, 

 hold the hot current close to the surface. 



The force of the wind at the surface of the earth is what concerns us, 

 and not its velocity at points of greater elevation, hence we may consider 

 how best to increase the height of the current. 



Sage brush deflects the wind from one to six feet, and prevents the sand 

 motions, enabling seeds of grasses and trees to germinate ; wild plum and 

 similar bushes raise it to a height of six to fifteen feet. An osage hedge not 

 cut back controls the currents to a height of twenty to thirty feet, while 

 a belt of Catalpa spcciosa, properly grown, will influence the wind to a height 

 of from fifty to one hundred feet. Eucalyptus, a hundred and fifty feet. But 

 these belts must be at frequent intervals to accomplish the desired result. 



To construct levees, dams and engineering works for the improvement 

 of navigable rivers, requires the authority and control of the government, 

 and aid of each state benefited. And this work, which would ameliorate the 

 condition of millions of our people, cannot be accomplished without the co- 

 operation of the national government, each state interested, and whole communities 

 of land owners. It will require patriotism and a high order of statesmanship 

 among legislators to prepare and enact laws releasing from taxation the 

 lands occupied by timber, and which will not be productive of an income for 

 the owner for several years, but it is worthy the effort. 



