4 68 POPULAR SCIENCE MONTHLY 



in the decade 1880-90, followed one of Bruckner's wet periods, and 

 the collapse of the 'boom' came when the drier period advanced. 

 Farmers who went out on to the high plains in the years of slightly 

 greater rainfall preceding the boom, and who lost all their capital, and 

 more too, in the vain attempt to raise their grain in the years which 

 followed, could with difficulty be convinced that the climate of the 

 plains had not permanently changed for the worse. The impression 

 left upon their minds, and upon the mind of anyone who saw the coun- 

 try later, was one of decreasing rainfall, unsuccessful agriculture and 

 financial ruin. Within more recent years, in this same region of 

 Kansas, with a somewhat increased rainfall during a wetter cycle, but 

 without any permanent change to a wetter climate, the intelligent 

 choice of cereals better adapted to the soil and climate, and the rational 

 use of the available water supply, have wrought a wonderful change 

 in the aspect and economic value of the state. 



The following table shows the dates and characters of Bruckner's 

 periods : 



Interesting confirmation of Bruckner's thirty-five-year period has 

 been found by Bichter in the variations of the Swiss glaciers, but as 

 these glaciers differ in length, they do not all advance and retreat at 

 the same time. The advance is seen during the cold and damp periods. 

 Sttpan has pointed out that the Bruckner periods appear to hold good 

 in the south polar regions. And Hann's study of the monthly and 

 annual means of rainfall at Padua (1725-1900), Klagenfurt (1813- 

 1900) and Milan (1764-1900) brings to light an alternation of 

 wet and dry periods in harmony with the thirty-five year cycle. 

 It should be noted that Bruckner has found certain districts in 

 which the phases and epochs of the climatic cycle are exactly re- 

 versed. These exceptional districts are almost altogether limited to 

 marine climates. There is thus a sort of compensation between oceans 

 and continents. The rainier periods on the continents are accom- 

 panied by relatively low pressures, while the pressures are high and 

 the period dry over the oceans, and vice versa. The cold and rainy 

 periods are also marked by a decrease in all pressure differences. It is 

 obvious that changes in the general distribution of atmospheric pres- 

 sures over extended areas, of the great centers of high and low pressure, 

 are closely associated with fluctuations in temperature and rainfall. 

 An oscillation of a few hundred miles one way or another may mean 

 the difference between drought or plentiful rainfall over extended areas. 

 These changes in pressure distribution must in some way be associated 



