IOWA ACADEMY OF SCIENCES. , 67 



many trips by rail through the tiooded district. The terrible 

 strength of the water flow then became apparent and, noting 

 the limited drainage area of Dry Branch in particular, I began 

 to take more interest in the event, believing at this time that 

 the real precipitation must be about five or six inches. I have 

 since made a thorough canvass of the county and record for 

 those interested in these phenomena only those things wh'ch 

 are beyond dispute. 



At 10 o'clock on Monday night, August 15th, it began to rain. 

 The precipitation was not extraordinarily heavy, and while it 

 rained steadily no one noticed that there was anything unusual 

 about it. According to good authority, the so-called cloud-burst 

 began about 2 o'clock a. m. and ceased shortly after 4. It 

 rained more or less for an hour later, however. A liberal esti- 

 mate of time for the heavy rain is three hours. The precipita- 

 tion outside of these three hours, from all accounts, could 

 hardly have been more than two inches. 



The area of heavy rainfall can be approximately bounded on 

 the south by the divide betw^een Spring creek and Flint river. 

 The former stream was not out of its banks. Keokuk reports 

 a trace only. The county line forms a close boundary on the 

 west, Yarmouth being in the edge of the heavy rain, but suf- 

 fered only from lightning. Washington reports 1.72; Iowa 

 City, .40. The north boundary of very heavy rain is not far 

 above the county line, Wapello reporting 5.16. On the east, 

 the river was the boundary for excessive rain, although the 

 precipitation was heavy as far east as Biggsville, 111. This 

 maps out two-thirds of Des Moines county, or approximately 

 250 square miles. The Flint river and its tributaries drain 

 one-half of this area. Dry Branch, Yellow SjDrings, Dolbee 

 and Swank creeks drain the remainder, save a strip of three 

 miles in width, which drains north into Louisa county. Dry 

 Branch drains only about eleven square miles, yet its waters 

 caused much damage. Yellow Springs creek drains a much 

 larger area and carried, perhaps, more water, proportionately 

 to its bed, than Dry Branch. 



It is not easy to estimate the rainfall accurately. There 

 were no rain gauges in the county at this time. I shall give 

 some of the reports as I obtained them. Great care has been 

 taken to get accurate and truthful accounts in this phase of the 

 investigation. 



