92 Notes on Hydrology. 



observed to be years of mean higher barometric pressure, 

 and has shown that in South Australia the seasons of 

 drought and floods follow in some sort of cycle. Mr. 

 Russell, of New South Wales, appears to attach some weight 

 to a nineteen-year cycle. I believe I am correct in stating 

 that in England, where they have the advantage of a very 

 extensive range of observations, no satisfactory cyclic series 

 can be arrived at : and I have never heard Mr. Ellery's 

 opinion respecting Victoria. 



Some years since I was under the impression that we had 

 a cycle of seven years, for the following reasons : — In 

 Melbourne, 1842 was a wet year and a year of floods ; 1849 

 the wettest in white man's time ; 1856, 1863, 1870, periods 

 of seven years, and very wet years — viz., 1842, 31 inches ; 

 1849, 42 inches; 1856, 30 inches; 1863, 36 inches; 1870, 33 

 inches; 27 inches being the average; but to upset the seven- 

 year i$ea, 1=875 was the wet year, with 33 inches, and 1877, 

 which ought to have been wet, only supplied 24 inches ; 

 so I gave up my long-cherished idea in disgust, and the 

 nineteen-j^ear theory will not apply. The dry years are 

 much more irregular. For a period extending from 1840 to 

 date, excepting a few years (1851 to 1854, no records), the 

 driest seven years have been — 1865, 15'9 inches; 1868, 18"2 

 inches; 1879, 192 inches; 1843, 215 inches; 1859, 21*8 

 inches ; 1862, 22'0 inches; 1866, 22-4 inches. 



The wettest seven years— 1849, 42'2 inches ; 1863, 364 

 inches; 1870, 337 inches; 1848, 331 inches; 1875, 32"8 

 inches ; 1872, 32*5 inches ; 1842, 311 inches. 



The number of wet days in a year varies greatly — from 

 107 days in 1866 to 165 days in 1863. 



In Sandhurst the average rainfall for twenty years is 

 217 inches, varying from 10'9 inches in 1865 to 38*3 inches 

 in 1870. The rains are fewer, and of shorter duration, as a 

 rule, than in Melbourne — in 1877, 64 days on which rain 

 fell ; 1876, 65 days ; the greatest number being 132 days, in 

 1863, the average being about 99 days a year. 



Rainfall, Sandhurst, 1861 to 1882. 



Average ... 21*73 inches per annum 



Least rain ... 10-95 „ in 1865 



Most rain ... 38*36 „ in 1870 



Rain = Average ... 2174 „ in 1867 



Seven years over average and twelve years under. 



