12 



INDIAN FOREST MEMOIRS. 



must recognise not one, but several, possible modes of origin, differing according to the 

 moisture content of the soil and to its initial sandy or clayey nature. 



ciimate. 40. As regards the climate of the locality 



dealt with, the details given below, which have been abstracted from the meteorological 

 records of Dehra Dun station, give some idea of the prevailing conditions. Dehra Dun, 

 as will be seen from the map, Plate I, is approximately in the centre of the Dehra Dun 

 valley and it is situated at an elevation of 2,233 feet above mean sea level. 



The area lying to the south of the Siwaliks receives less rainfall, averaging from 30 to 

 50 inches only per annum, and also possesses a more severe climate with a uniformly 

 higher average shade maximum temperature throughout the year and with a lower average 

 minimum shade temperature in December and January. 



>> 



3 



5 



«-5 



February. 





■3* 





s 





3 

 < 



September. 



"o 

 o 

 O 



o\ : November, 



6 



December. 



CD 



81-1 



Description of Statistics. 



66-2 



69-2 



797 



90-6 



95-0 



93-0 



85-5 



84-0 



84-3 



82-3 



68-7 



Average monthly and annual 

 means of maximum shade 

 temperature in degrees 

 Fahrenheit from observa- 

 tions for period 1875 — 

 1899. 



44-8 



47'0 



550 



64-3 



705 



74-4 



741 



73-1 



700 



606 



51-8 



456 



60-9 



Average monthly and annual 

 means of minimum shade 

 temperature. 



546 



576 



67-0 



77-4 



81*6 



82-2 



78-7 



77-3 



76-1 



70-7 



62-6 



56-3 



70-1 



Average monthly and annual 

 means of shade tempera- 

 ture corrected to true 

 diurnal means obtained 

 from the above maximum 

 and minimum data, a cor- 

 rection obtained from 

 hourly observation data 

 being applied. 



2-26 



204 



116 



0-65 



1-45 



909 



25-98 



26-31 



8-97 



083 



21 



0-68 



79-63 



Average monthly and annual 

 rainfall (in inches) calcu- 

 lated from all available 

 data down to 1900. 



Per cent. 



Per cent. 



Per 



cent. 



Per 



cent. 



Per 



cent. 



Per 



cent. 



Per 

 cent. 



Pel- 

 cent. 



Per cent. 



Per 

 cent. 



Per cent. 



Per cent. 



Per cent. 





669 



61-9 



47 - 4 



37-4 



40-5 



62-1 



85-5 



90-6 



821 



65-6 



62-8 



628 



63-8 



Average monthly and annual 

 means of relative humidity 

 corrected to true diurnal 

 means, based on the data 

 available for the period 

 1877—1902. 



The highest absolute maximum shade temperature recorded at Dehra Dun previous to 1903 is 111° registered in June. 

 .. lowest „ minimum ,, „ „ „ „ „ ,, ,, 33-9° „ „ February. 



[ 42 ] 



