360 METEOROLOGY OF BEHAR HILLS, &c. Appendix A. 



the number of hours or rather of parts of each hour, that the sun 

 shines, and its clearness during the time. To secure valuable results 

 this should be done repeatedly, and the strength of the rays by the 

 black-bulb thermometer registered at each hour. The few actino- 

 meter observations will be found in another part of the Appendix. 



The dew-point has been calculated from the wet-bulb, by 

 Dr. Apjohn's formula, or, where the depression of the barometer 

 is considerable, by that as modified by Colonel Boileau. * The 

 saturation-point was obtained by dividing the tension at the 

 dew-point by that at the ordinary temperature, and the weight of 

 vapour, by Daniell's formula. 



The following summary of meteorological observations is alluded 

 to at vol. i., p. 15. 



I.- — Table-land of Birbhoom and JBehar,from Taldan<jato Dunwah. 

 Average elevation 1,135 feet. 



It is evident from these observations, that compared with Calcutta, 

 the dryness of the atmosphere is the most remarkable feature of this 

 table-land, the temperature not being high; and to this, combined with 

 the sterility of the soil over a great part of the surface, must be 

 attributed the want of a vigorous vegetation. Though so favourably 

 exposed to the influence of nocturnal radiation, the amount of the 

 latter is small. The maximum depression of a thermometer laid on 

 grass never exceeded 10°, and averaged 7° ; whereas the average 

 depression of the dew-point at the same hour amounted to 25° in 

 the morning. Of course no dew was deposited even in the clearest 

 star-light night. 



* Journal of Asiatic Society, No, 147 (1844), p. 135. 



