54 THE CLIMATE OF AUSTRALASIA 



about 35 years ; and Hann's more recent, and 

 still more detailed study of the rainfall of Padua 

 since 1725, and of Milan since 1764, has con- 

 firmed Bruckner's conclusion.! 



Bruckner's study of the rainfall, therefore, 

 showed that the variation of the lakes was the 

 result of the variation in the rainfall. Thus the 

 ake levels were lowest in 1720, 1760, i8oc 

 1835, 1865; they were highest in 1740, 1780, 

 1820, 1850, and 1880. Bruckner found that 

 there were dry periods in 1831-40, 1861-65, anc ^ 

 wet periods from 1846-55 and 1876-80. So the 

 lakes were at their highest, at about the time of 

 the wet periods. 



As rain is a product of distillation, variations 

 in its amount probably indicate periods of warm 

 and cold weather. Bruckner, therefore, en- 

 quired whether there was any connection 

 between the temperature records and these dry 

 and wet periods. He found that from 1736- 

 1885 there has been the same 34-35 years cycle 

 of variation in temperature. Severe winters 

 and the freezing over of European rivers are 

 recorded in history since early times ; records 

 are available as far back as the year 800, but 

 they are too incomplete to be of much use 

 before the year 1000 ; and the records show a 

 temperature variation of the same length as the 

 rainfall and the lake levels. Thus, Bruckner 

 finds that there were cold periods from 1591- 

 1600, 1611-35, ^646-65, 1691-1715, 1730-1750, 



fllann's Memoir is published in Sitzber. K. Akad. Wien., vol. 

 CXI. II. a, 1902, pp. 1-120. 



