352 



The Meleo7'ology of the Plains 



lower station, Lecome more condensed, and thus having their capacity 

 for heat diminished, give out a portion of their latent caloric, which 

 necessarily prevents the sinking of the temperature to the degree it 

 otherwise would, in consequence of the cooling effect of radiation from 

 the surface of the soil. Favoured as this procebS is by the stillness 

 and clearness of the night, its effects would be more perceptible, did 

 not the breadth of the ridge bear but a small proportion to the mass of 

 the air by which it is surrounded. This equabiliiy of temperature is 

 observed, not only from day to night, but also from hour to hour, and 

 from summer to winter. 



One great anomaly presents itself inconsequence of ihe still calm- 

 ness of the mornings; for though the nights are pleasant and the morn- 

 ings cool, yet, from the rapid rise of the sun, and the great power of 

 the solar rays, the heat becomes considerable, and even insupportable in 

 the open air, until a gentle breeze rises, and ascending up the valley, 

 continues through the day, apparently following the course of the sun. 

 The maximum of temperature frequently occuis at ten, or, at all events, 

 the increase after that is so slight as not to be perceptible to the senses. 

 In the plains we know the temperature of the air goes on increasing 

 until 2 or 3 p. m. As the latitude is nearly the same as that of Saha- 

 runpore, the power of the solar rays and the quantity of heat commu- 

 nicated in a given time must be nearly the same ; but in the plains it is 

 allowed to accumulate: in the hills, on the contrary, the breeze which 

 sets in daily from the plains towards the hills, and which commences 

 about 10 A. M. (the very time after which so little increase takes place 

 in temperature), passes over the top of the range, and prevents the ac- 

 cumulation of any heat. This breeze, though caused by the heat of the 

 sun rarefying the dense air, at the surface of the earth, might be ex- 

 pected to arrive at the mountain top in the hot and parched state in 

 which it rose from the heated plains ; but the air as it ascends becomes 

 still less dense, and in proportion to this diminution of density is its 

 capacity for heat increased ; so that it absorbs all the caloric which, in 

 the plains, was sensible to the feelings, or was observed by a thermo- 

 meter, and thus, on arriving at the top of the range, it feels cool and 

 refreshing.* At night, a similar, but more gentle breeze, sets in from 

 the hills towards the plains, and the two may, with the strictest justice, 

 be compared to the land and sea breezes of the Coast and of Equatorial 

 islands. 



• These observations were first published by the Author in a Paper read befoie th» 

 Asiatic Society ol Calcutta, and ostiacts pubUsbed iu the Jouin. As. Soc, vol. i, p, 07, 



