36 



J. HOPErNSON HEETFOEDSHIHE EATNFALL, 



Dividins,' the half-ccntiiiy into five periods of ten years each, "O'e 



have the following result : — 



The rainfall during the first and third decade was thus appreci- 

 al'ly below the mean for the half-century, during the fourth decade 

 considerably above the mean, and during the second and fifth 

 decades very near the mean. The winter rainfall shows a con- 

 siderable increase in recent years, for during the first and second 

 decades together it averaged 5 per cent, in defect of the mean for 

 the half-century, and during the fourth and fifth decades together, 

 5 per cent, in excess of the mean, being very near the mean dm'ing 

 the third decade. 



The progressive increase in the rainfall during the half -century, 

 if longer periods than decades are considered, may be clearly shown 

 bv taking successive periods of twenty years ending 1862, 1872, 

 1882, and 1892, thus:— 



If reliance can be placed on very old records, it would seem that 

 there has been a slight increase in the rainfall in the south-east 

 of England during the last century, that is to say, that the rainfall 

 during the fifty years 1842-92 was greater than during the fifty 

 years 1792-1842, but half a century is a sufficiently long period for 

 the purpose of this inqiiiiy. It must not, however, be presumed 

 that there is a secular increase in the rainfall which is likely to 

 continue, for there are many considerations which would lead us to 

 infer that the reverse is the case, the heavy rainfall of recent years 



