70 



Rainfall, Natural Drainage, 



The mean rainfall at Greenwich for the period in question 

 was 25 '22 inches only. The largest rainfall was in 1824, and 

 amounted to 36"3 inches. The lowest was 16'3 inches, and 



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occurred in 1864. The extreme amount of range in different 

 years is thus 20 inches, or more than half the maximum. The 

 diagram marked II. will exhibit the facts recorded in the simplest 

 and best manner. 



From tabular statements of this nature it necessarily requires 



