DEW, HOARFROST, ELECTRICITY. 



441 



the ground or in the air, this last may have been derived from the 

 ground. If neither the ground nor the air contain moisture, no 

 dews can exist, this is the case in Khorassan. 



Throughout the whole campaign no dews were noticed, although 

 the nights were almost uniformly serene, and calm, and the time 

 chosen for marching, would have certainly brought us in contact 

 with them had they been deposited. Dews therefore do not form 

 in Khorassan, with these exceptions, that wherever from the nature, 

 and the level of the soil, water was found very near the surface, dews 

 were deposited ; as on the Chummums or low marshy pasturages at 

 Candahar, Cabul, etc. 



But even these were trifling, the aridity of the air being too great as 

 compared with the small extent of Chummums, to allow the deposit 

 of any considerable portion of the moisture it had derived from the 

 ground. 



So that aridity, instead of being adapted to dews, is a serious obstacle 

 to their ever appearing. With the rarity of dew, that of hoarfrost 

 which is nothing but frozen dew, may be associated ; nor does hoar 

 frost often occur, because in Khorassan it rains in the winter too 

 freely, particularly in all such places whose elevation is not sufficient 

 to cause the formation of snow, and hence where other circumstances 

 are favourable for hoarfrosts, they are too much watered as it were, 

 and seldom occur. With extreme aridity, Khorassan unites ex- 

 treme electricity, the casual friction of woollen cloths, especially 

 those of camels' hair being accompanied by discharges sufficiently 

 startling. The same thing happens when caressing dogs or horses. 

 I could never fill the barometer without experiencing a shock as the 

 mercury approached the bottom end of the tube, which (when ner- 

 vous) used to endanger it. 



It is this extreme aridity that gives Khorassan so rich a spring 

 flora, this season being that of rain, of melting of snow, and the 

 ground being well moistened. 



It is this extreme aridity that necessitates the abundance of bul- 

 bous plants in Khorassan, these deposits of nutrition existing even 

 in several of its Compositse. 



Query — Why are Carduacese, (Artemisia) so adapted to aridity ? 



The region of Carduacese, commences about Ghuzni, and extends 

 to Maidan or Cabul, it is at its maximum about Shaikabad and Huf- 

 tasya. The abundance of Carduaceae on the higher grounds, as for 

 instance towards Bamean, belong rather to a vernal flora. 



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