202 A. N. Pearson — Variations of Rainfall in Northern [No. 3, 



Tlie smoothed numbers of the above table are curved in the accom- 

 panying diagram (PI. XI) in thick continuous lines, under the names 

 " Winter Rainfall, A" and " Summer Rainfall, B." The figures so pro- 

 duced are identical with the curves given by Mr. Hill in his paper. The 

 unsmoothed numbers of the above table are in the diagram superposed in 

 dotted lines upon the smoothed curves. At the bottom of the diagram, 

 T have reproduced the sunspot curve as given by Mr. Hill. 



On inspecting the smoothed rainfall curves, it will be seen that the 

 winter and the summer curve both agree in showing a single oscillation 

 during the eleven years of the sunspot period ; but they differ in the 

 character of that oscillation, for, while the winter rainfall is at its maxi- 

 mum during the year of sunspot minimum, the summer rainfall on the 

 contrary is then at a minimum. This is the main fact pointed out in 

 the paper above quoted. 



On inspecting the actual figures, however, — the unsmoothed num- 

 bers in the above table and the dotted curves A and B of the dia- 

 gram — it will be seen that, besides this eleven yearly oscillation, both 

 the winter and the summer rainfall show several variations of minor 

 period such as one might naturally suppose to be accidental ; thus the 

 winter rainfall shows three distinct maxima, one in the 2nd year of 

 the sunspot cycle, one in the 7th year, and one in the 9th and 10th, and 

 shows marked minima in the 3rd, 8th, and 11th years ; while the summer 

 rainfall has maxima in the 2nd, 4th, and 8th years and minima in the 3rd, 

 7th, and 9th. 



It is to these minor period oscillations that I wish in this short 

 paper to call attention. And, in order that they may present themselves 

 in a more convenient form for study, I have separated them from the 

 eleven yearly oscillation by the simple method of subtracting the 

 smoothed numbers in the above table from the unsmoothed. The 

 differences are curved in the diagram under the name " Minor Oscilla- 

 tions of A and B," the winter oscillations being given in dot-and-dash 

 lines, and the summer in simple dotted lines. 



Confining attention to these " minor oscillations " curves, it will be 

 noticed that, in those years which at the foot of the diagram are marked 

 + , and which are years of maximum sunspot, the short period oscilla- 

 tions in the winter and the summer rainfall are of the same character, 

 that is to say, that when there is more winter rain there is more summer 

 rain, and when there is less of the one there is less of the other also. 

 But it will be seen that, in those years which at the foot of the diagram 

 are marked — , and which are years of minimum sunspot, the short 

 period oscillations in the winter rainfall are of opposite character to those 

 in the summer rainfall, that when there is more rain in the winter there 



