ON THE RAINFALL OF THE BRITISH ISLES. 



103 



have twelve perfect records at widely separated stations. The mean fall in 

 each decade and in the whole period, and the ratio of each decade to the 

 whole period at each station, is given ia Table III. 



From careful examination of Table III., it appears that the amount of 

 rain which fell in the ten years 1830-39 was very similar to that which 

 fell in the ten following years, the difference being a decrease, but scarcely 

 one per cent. The investigation in our 1866 Report shows an increase of 

 1-2 per cent. ; and examination of returns ceasing in 1850, and therefore not 

 quoted in either Report, show several cases of absolute identity. 



With one investigation leading to a decrease of 1 per cent., another to an 

 increase of the same amount, and a third to identity, we are led to the con- 

 clusion that the two decades may be considered to show similar results. 

 This is a much more important fact than it at first appears ; and for this 



Table III. — Comparison of the Rainfall in each Decade since 1829 with 

 the Mean Rainfall of forty years, ending with 1869. 



