oct. — MAE. 1859-60.] Parvaiipore and Jeypors. 



289 



to the cold currents. In this manner then there is a constant 

 movement in the atmosphere, the currents of cold air descending 

 the mountain side3, and the steam of hot air laterally- 

 forced to the centre of the valley, where thsy mingle and 

 ascend. This is I conceive the probable cause of the above 

 phenomenon, and if the foregoing reasoning holds good, it 

 would follow that in narrow villages bounded by high hills, the 

 temperature would be sensibly lower than in those distinguished 

 by the opposite characteristics, and this we invariably found to be 

 true. In the case of the great longitudinal valleys of the Plateau 

 the hot air forced along them by the cold air descending the great 

 mountain chain, meets with little or no opposing similar current 

 which compels it abruptly to seek an upward course, and it there- 

 fore flows along these valleys gradually becoming warmer by the 

 reception of radiated heat from the ground over which it passes, 

 and then rises and mingles with the superincumbent atmosphere. 

 It is of course followed by the cold air, which also gradually be- 

 comes warmer and rises. According to this theory the farther we 

 recede from the chain of high hills, and approach the W. bounda- 

 ry of the Plateau, the minimum of the thermometer will ascend, 

 and this we also found to be the case. The healthiest situations 

 then, and those most eligible for occupation are the wide and ex- 

 tensive valleys, bounded by low bare hills, which are common in 

 the centre and toward the W. edge of the Plateau ; although these 

 are by no means beyond fever range, yet there is nothing at hand 

 which can generate malaria, and it is difficult to conceive that 

 with ordinary precaution Europeans might not pass there with 

 perfect immunity from fever the whole year round. The principal 

 precaution to be observed is to avoid sleeping on the ground, and 

 indeed we should sleep as high above it as can be, as wherever 

 malaria does exist, and it is supposed to be principally owing 

 to the presence of a redundance in the atmosphere of Carbonic 

 acid, a gas of a specific gravity considerably greater than the air, 

 and therefore found principally in its lower strata, it is invariably 

 found that those who habitually sleep close to, or on the ground 

 rarely escape it, whereas those who sleep well above the ground 

 do so very commonly. 



