32 



causes a very rapid evaporation to take place almost immediately. Hence, 

 during the hot mouths, a number of secondary showers quite often fol- 

 lowed a thunder-storm under forested conditions. The old weather adage 

 that "Fog rising from the hills will soon give water to the mills," seldom 

 failed of fulfillment. The benefits derived from the more gently falling 

 showers following the hard downpour of the thunder-storm in filling the 

 soil of the cultivated fields and pasture lands can hardly be estimated. 

 It is the moisture from these rains that adds very greatly to the ground 

 water, especially on the firmer earth surfaces. 



Again, if it be true, as now appears from records kept during the last 

 ten years, that the summer rainfall of the trans-Mississippi states, par- 

 ticularly Oklahoma, Kansas and Nebraska, be increasing, it would uphold 

 the theory just advanced. In contrast with the naked prairie of the past, 

 which had a large immediate run off, the plowed lands of today are a 

 much better absorber of moisture, and would increase very much the ground 

 water supply. The early summer cultivation of extensive cornfields would 

 tend to conserve this moisture, until the rank growth of corn or other 

 cultivated vegetation, with its extensive leaf surface, would add greatly 

 to the evaporating surface. This would increase the local atmospheric 

 moisture, especially during July and August. Hence, if the above theory 

 be true, there should be ordinarily an ever-increasing rainfall during those 

 months year by year, just in proportion to the area of original prairie 

 land put under cultivation. If trees were more extensively planted, the 

 results in increased rainfall should be marked to the same degree. 



In resume, we may say that theory upholds, and observation sub- 

 stantiates the statement, that deforestation greatly increases the immedi 

 ate run off, and as greatly decreases the ground-water supply of a given 

 region. It is equally true that the absence of forests seriously decreases 

 the evaporation, and the amount of vapor in the atmosphere, during the 

 hot months. Again, the absence of evaporation permits of higher local 

 temperatures on the approach of low barometric areas and hence the rela- 

 tive humidity of the atmosphere must be lower. All tend toward the re- 

 duction of the rainfall during the late summer months, when of all times 

 it is most needed for the growth and maturing of vegetation. 



Furthermore, we believe that it can be shown that deforestation has 

 a tendency in a region of rough topography, such as is found among the 

 hills of southern Indiana, to localize the hot season rainfall, and to pro- 

 duce conditions approximating those of the so-called "cloudbursts" of the 



