406 KANSAS CITY REVIEW OF SCIENCE. 



The last decade of September was very wet ; over four inches having fallen 

 in one rain on the 27th and 28th. The rains of October have not been excessive^ 

 but with the previous saturated condition of the soil a small amount has kept the 

 tilled fields very moist, and potatoes have rotted in consequence. 



The red sunsets have been scarcely inferior to those of last year at this time, 

 which first attracted the attention of the scientific world. They have seemed most. 

 brilHant on those evenings which succeeded heavy rains, and this is another reason 

 for thinking the moisture largely concerned in their production. This of course 

 does not militate against the volcanic dust theory which furnishes the nuclei 

 around which these water particles can condense at high elevation. 



ST. LOUIS ACADEMY OF SCIENCE. 



The Academy of Science held its first meeting since the summer vacation at 

 Washington University, October 6th. Prof. Nipher read a paper on the relation 

 between the violence and duration of maximum rains. 



His data was taken from Dr. Engelmann's observations, lasting over a period 

 of forty-seven years. The violence of the rain is measured by the amount of 

 rain falling per hour. Taking only the heaviest and longest rains during the 

 above period of time, each rain is represented on a diagram by a point, if the 

 duration and violence of the rain are taken as co-ordinates. It was found that 

 rains of great violence lasted a comparatively short time, while gentle rains of a. 

 quarter of an inch per hour may possibly last a long time — as much as twenty 

 hours in extreme cases. When all the points representing all the rains had been 

 plotted on the diagram, it was found that a curve passing through the outermost 

 points, representing the rains where the greatest amount of water falls, is an equi- 

 lateral hyperbola. This means that the duration of maximum rains is inversely 

 proportional to the violence, or that the product of violence into duration is con- 

 stant. This constant is the amount of water which may fall in a continuous rain, 

 and is, for Dr. Engelmann's series of about half a century, about five inches. A 

 rain of five inches per hour may last one hour, a rain of four inches per hour 

 may last an hour and a quarter, and such a rain Dr. Engelmann observed. A 

 rain of two and a half inches may last two hours, and several such rains were 

 observed. A rain of an inch per hour may last five hours. Each of these cases 

 would be a five-inch rain. For a longer period of time than fifty years it is likely 

 that greater rains than five inches may be observed. The same is to be said if 

 observations are to be taken over a wider area of country. In fact, a rain of 

 six inches in three hours occurred near Cuba, Mo., some years since. This 

 would increase the value of the constant from five to six, but otherwise the rela- 

 tion will probably remain unchanged. 



The importance of this law is very great in engineering, where the capacity 

 of sewers, culverts and bridges must be such as to carry the water. A more gen- 

 eral investigation, which Prof. Nipher is now making, will determine the relation 



