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Cincinnati Society of Natural History. 



which is deducible from a statistical consideration of the record of the 

 past fifty two years. 



The total number of floods from 1832 to 1884 inclusive, reaching above 

 50 feet of water in the channel, is fifteen, or one every three and a half 

 years, on the average. 



One occurred in 1875 under continued and unusual rainfall (very ex- 

 ceptional conditions), in August. 



One occurred in December, 1847. 



Two occurred in March, 1865, 1867. 



Four occurred in January, 1862, 1870, 1876, 1877. 



All the remaining seven occurred in the month of February. 



A period, embracing from December 15th to March 15th, includes all the 

 floods but one for the whole period of fifty-two years ; while a shorter 

 period, from January 15th to March 1st, includes all but four. December, 

 January, February and March are the months'of the year when the floods 

 are to be looked for, and in this seasonal differentiation, so strongly marked 

 by the record for t more than fifty years, we must look for a factor which, 

 when added to the amount of rainfall, will aid us to the solution of the 

 problem. 



We have this factor in the agency of cold. It precipitates moisture in 

 the form of snow, allows it to thus accumulate in immense banks in mount- 

 ains and valleys; throughout the entire basin vast quantities are thus 

 piled up. The ground beneath is also frozen, and thus becomes impervious 

 to water, which can not disappear in it. 



The third and great factor is to be found from a careful study of meteor- 

 ological observations, which have been compiled in recent years through 

 our valuable Signal Service. A very valuable pamphlet upon the weather, 

 by S. S. Bassler, Esq., has recently been published in Cincinnati, and it 

 especially points out the fact that storms are areas of low barometer, which 

 travel along broad, through pretty distinct and well-beaten paths. The Ohio 

 Valley is the track of storms from the Grulf of Mexico and from the great 

 Northwest. During the winter months this is especially true. One or two 

 cold storms, with snow from the Northwest, are followed by warm storms 

 with rain from the Grulf. Thus we find ourselves in the track of both cold 

 and warm storms ; and so constant and sudden is the predominance of first 

 one, and then the other, that we are in a climate of perpetual and rapid 

 change. 



The conditions as regard banked snow are often present for a flood. You 

 will all recall that upon December 22, 1883, a great amount of snow fell. 

 Tt was settled by several inches of fine hail, so that the amount of con. 



