84 



the six or- eight square miles covered by the storm, but the hot air from 

 the proximity, on reaching this area of rapidly rising atmosphere, con- 

 stantly added its moisture to that being condensed, with the result that 

 for two hours the downpour continued. This very unusual precipitation 

 proved exceedingly disastrous to the soil of the cultivated fields, and to 

 the roads and bridges as well as to property of all kinds along Brushy- 

 fork Creek and the larger tributaries of Indian Creek. Both of these 

 streams were several feet above any previous record. Where a few mo- 

 ments before there were dry, rocky creek beds, now became a wild flood 

 from six to ten feet in depth and from 3O0 to 500 feet wide. Buildings 

 were carried away that had seldom or never been touched by previous 

 floods. 



In the opinion of the writer this cloudburst, which in truth it was, 

 was caused by the intense heating of the deforested region of very rough 

 topography to the southwest, followed by the gentle movement of great 

 volumes of heated air in a northeasterly direction, until in its passage 

 over the divide it rapidly ascended. Becoming cooled in its ascent, the 

 enormous quantity of moisture held in the highly-heated atmosphere rap- 

 idly condensed, and the unprecedented rainfall for that region followed. 

 It may be years before conditions of temperature, moisture and winds 

 would unite to produce another such storm in the same locality, yet the 

 probabilities are that in the future such rainfalls will become increas- 

 ingly frequent somewhere in such deforested areas of rough topography. 



From observations in the Rocky Mountains of Colorado and Wyoming, 

 the cloudbursts of those regions are formed under essentially similar con- 

 ditions, so far as the absence of forests and areas of highly-heated air are 

 concerned. In the mountains, however, these storms may be more intense, 

 and more frequent, because of the greater height of the divides and the 

 almost entire absence of vegetation or even of any considerable mantle 

 of soil. 



Observation of the hill region of southern Indiana compels one to 

 believe that as the forest growth has disappeared such storms have be- 

 come more prevalent. Excessive rainfall occurs over limited areas, whil^ 

 drouth conditions prevail over the surrounding country. In the one place 

 of rainfall the destruction caused by the flood may be even more dis- 

 astrous than the continued drouth over the nearby territory. 



The effect of forest destruction upon streams has often been described 

 and need not be dwelt upon in this paper at any length. In the area 



