General Considerations . 



211 



have their origin at a far greater distance from us, viz., in 

 the tropics. These simoons in Missouri always blow from 

 the southwest, in Kansas from south-southwest, and in 

 Eastern Colorado south, or a few points east of south; 

 and their injurious and scorching effects are not infre- 

 quently felt before the frost in Kansas and the country to 

 the west is fairly out of the ground. 



2. It is well known that the buffalo grass ranges over a 

 vast extent of our Western plains, and that it does not 

 furnish a very dense or thorough covering, even when 

 unburned, and assists very little in retaining moisture or 

 preventing evaporation. 



3. My own observations for the past seventeen years in 

 this Western prairie country lead me to the conclusion 

 that fires more often succeed than precede drouth, and that 

 they may more justly be looked upon as a result than as a 

 cause of excessive dry weather; and the prevailing belief 

 that large conflagrations or extensive fires are conducive 

 to rain, bears on this point. 



4. Whenever grass is burned during the growing 

 season, the old and drier blade is soon succeeded by a green 

 and succulent one, which has far greater power to attract 

 and retain moisture; while if burned in winter time the 

 evaporation from the soil can be thereby but slightly 

 affected, because of the weakened power of the sun, and 

 the snows which usually cover and protect. 



5. Drouths are by no means confined to that portion of 

 the country subject to the locust invasions. 



6. The reason why locusts are more sluggish and less 

 inclined to fly at morn than at noon is not so much a ques- 

 tion of the comparative density of the atmosphere as of 

 the difference in temperature. All diurnal insects are 

 sluggish in the cool of the morning, and their activity 

 increases with the rising of the thermometer; and flight, 



