254 3Ir. Dalton on Metfcorohgy. [April, 



Now, by blending these 17 years with the 8 years before 

 referred to, we obtain the mean monthly averages for 25 years, 

 as under ; namely, 



Inches. 



January 2-258 



February. 2'507 



March 2-112 



April 1-915 



May 2-698 



June 2-206 



July 3-400 



August 3-307 



September 2-984 



October. 3-734 



November 3-378 



December 3-369 



Total 33-868 



I think there is reason to believe that if we had the averagces 

 for a century, they would not be materially different from these, 

 either in regard to the relative monthly quantities, or to the 

 annual quantity. 



It may be proper, however, to obsei-ve, that the late Mr. 

 George Walker, of Salford, gives an account of the rain at 

 Manchester, for the nine years immediately preceding the above 

 period of 25 years, in the Memoirs, vol. iv. p. 585. His obser- 

 vations have been incorporated with mine so as to extend the 

 period from a quarter to a third of a century ; but I prefer having 

 his results separate, for the following reasons. On a comparison 

 of our results for eight subsequent years, I found his average 

 exceeded mine by about four inches in the year. (See Memoirs, 

 vol. V. p. 668.) On inspecting his gauge, I had reason to think 

 his mode of measuring the rain was not susceptible of sufficient 

 accuracy, and suggested the same to him, Avith which he seemed 

 to acquiesce. Besides this, the year 1792 (one of the eight) was 

 a most remarkable one, in the north of England particularly. 

 The annual depth exceeded the average amazingly ; and it was 

 occasioned by an excess in tv/o or three of the months chiefly. 

 The rain at Kendal that year was nearly 85 inches ; and it was 

 nearly the same at Keswick. April produced 10 inches, Sep- 

 tember 11 inches, and December 12 inches. Mr. Walker's rain 

 in Manchester that year was 55J- inches, wliich is far above the 

 average ; and nearly one half of this great quantity fell in three 

 months ; namely. May, September, and December. The year 

 1789 was also unusually wet. These facts influence the annual 

 and monthly averages of Mr. Walker materially, independently 

 of any supposed error in the actual measurement. 



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