Influence of Local Agents in the Production of Thunderstorms. 439 



If we suppose the Pontic atmosphere, coming from W.N.W. 

 at considerable altitudes, to pass over the Taurian Highlands, 

 radiating heat in consequence of protracted insolation, it must 

 become saturated nearly to its maximum with aqueous vapour 

 and receive a notable amount of negative electricity. Whenever 

 this atmosphere meets with the colossal prominence of Ararat, 

 the electricity of the clouds, accumulated in the aqueous vapour, 

 is suddenly increased; and, of course, electrical compensation 

 begins first on the north-west side of the Great Ararat. The 

 elliptical form and the situation of summit and ridge of Ararat 

 force the accumulated atmospheric current coming towards its 

 side to the broad elevated valley between the two Ararats, and to 

 its opening into the region where the atmosphere arising from 

 the hot south portion of the Araxes-plain has reached its maxi- 

 mum of heat and dryness. 



The greater half of the Lesser Ararat, whose base is notably 

 inclined east-north-eastward, and which rises to more than 9000 

 feet above the plain of the Araxes*, is almost to its summit 

 under the action of this pure and non-electric atmosphere, moving 

 constantly south-eastwards, and counteracted by a cold north- 

 west current descending from the depression between the two 

 mountain-groups (altitude 8274 feet) . The notable energy of this 

 counter-current is a necessary consequence of the local thermal 

 contrast between the summit-region and the neighbouring heated 

 plain. The uncommonly rapid decline of temperature observed on 

 the higher horizons of this valley is indicative of an accelerated 

 fall of the higher strata of clouds, containing (as M. Vogel sup- 

 poses) aqueous vapour of a temperature far below the point of 

 congelation, and the presence of which causes the violent falls of 

 hail, attending in most cases the thunderstorms breaking out in 

 the lower half of the valley. The clouds, highly charged with elec- 

 tricity, coming rapidly from the Great Ararat and turning round 

 the mountain, discharge each other on the north and east side of 

 the Lesser Ararat, as the difference between the temperature and 

 the point of degelation of the air in those regions increases with 

 the distance from the mountain towards the plain. At the same 

 time the increased permanent electro-negative tension of the 

 summit of the Lesser Ararat discharges the latent electricity of 

 the vapours, and provokes a continued intense compensation 

 with the electrically charged clouds constantly coming from the 

 Great Ararat. At all events, the degree of freedom from vapour 

 of the atmosphere above the Nachitshevan half of the Araxes 

 plain, as resulting from preceding meteorological conditions, 

 and consequently its degree of electrical conductibility, must 



* Absolute altitude of the Araxes plain in the meridian of the Great 

 Ararat, about 2400 feet. 



