Reduction of Meteorological Tables in the Doab. 425 



Min. of October 66° Mean, of Oct. 74.38 Max. of Oct. 80. 

 Min. of 1837, 67 Mean, of 1837, 74.31 Max. of 1837, 79.375 

 —1 -I- 0.07 + 0.625 



In the Kulsea observations for the same year, the Temperature 

 of the month of September, approached most closely to that of the 

 year. 



The expression, monthly differential, has been introduced to mark 

 the difference between the mean Temperature of each month and 

 that of the whole year, from which it appears that while the month of 

 July rises highest above the annual mean, December falls lowest, the 

 combined differences shewing a mean range of 37.91°. 



The influence of a fall of rain in decreasing the Temperature is 

 occasionally remarkably distinct. Thus on the 22nd of June 1837, 

 the Thermometer at sunrise was 85°; a fall of rain of 2.1 inches, but 

 so strictly local, that it was confined to within a few miles from 

 Surrowli took place on that day, and next morning the Thermo- 

 meter had sunk to 81°, shewing a difference of 4°, due undoubtedly 

 to the influence of the rain. Again on the 21st of July, the Thermo- 

 meter was 88°, showers fell on the same and two succeeding days, 

 and on the 24th the Temperature had fallen 6°. The cooling in- 

 fluence of rain may be shewn more in detail as follows, the instances 



being selected for the year 1837 







Temp, before rain. 



Temp, after rain. 



Diff. 



Fall of rain. 



1 85° 



81° 



4° . 



. 2.15 Inches. 



2 84° 



. 82° 



2 . 



. .525 



3 88° 





6 .. . 



, . .21 





. 78° 



4 .. . 



.11 





. 78° 



9 



.. 1.12 „ 







4 .. . 



.. .22 „ 













29 



9.1 95 



From the above it appears, that the cooling influence of a fall of 

 rain of 3.17 inches, reduces the Temperature 1° of Fahrenheit. Of 

 course so many local circumstances must necessarily affect this 

 result, that in the present instance it is no doubt more curious than 

 correct. 



3 H 



