178 THE RAINFALL AT BRISBANE, 
or 1881, and 1876+9 or 1885, should have proved moderately 
wet years. As far as the year 188] was concerned, this was true, 
but not so for 1885, as I will hereafter explain. 
As regards the minimal rainfalls, I find that their cycle is 
also 3 years, so that roughly speaking two wet years and a dry 
year are following each other periodically ; and furthermore, 
that those dry years Increase in intensity the more they recede 
from their point of culmination as a minimum, and also decrease 
in severity the more they approach the next point of minimum- 
culmination. By connecting all the ordinates of those years which 
proved to be dry with a curve, as also shown [BY A DOTTED LINE] 
on Plate VII., I obtained a distinctly marked - undulating 
periodical curve of 15 years cycle, so that, according to the 
figure, maximal or disastrous droughts appeared in 1862, 1865— 
and in 1862+15 or 1877, and L865+15=1880-81. We there- 
fore may expect the next disastrous droughts in 1877+15 or 
1892, and 1880 +15=1895. 
Before I enter into the disturbance of my curve during the 
years 1881—1885 I will draw attention to Plate VIII. which 
represents the cycles by closed, instead of continuous curves as 
before :—The cycle or circle is divided into nine equal parts by 
radii, and the amount of each year’s rain is expressed in polar- 
co-ordinates at = 5 scale. The cycle marked (————) 
represents the 9 years from 1860 tu 69; the second or cycle 
marked (------- ), those from 1869 to ’78; and lastly, the 
third cycle ( ), those from 1878 up to 1884. All of these 
cycles close wonderfully well in the years 1860,’ 1869, and 
1878. As will be seeu, each curve has, three prominences 
and three depressions at nearly the same cyclar year, 
so that maxima of rainfalls occurred in the years 1861, 
1870, and 1879; furthermore, in 1864, 1873, and also 
1882 moderately, and lastly in 1867, 1876, and—should have 
occurred—in 1885. On the other hand, minima of rainfalls 
occurred, according to the depressions of the cyclar curves, at 
