RAIN. 459 



but little supply of moisture to the atmosphere. Dense, na- 

 tive forests, and extensive wastes of shrub and bush-growth, 

 cover the greater part of the surfaces of the higher ranges 

 of knobs and slopes. This, of course, prevents the sun's 

 rays and winds from acting on the water of the soil, and 

 therefore quick surface evaporation, to the extent which oc- 

 curs in cleared and cultivated regions, cannot here take 

 place. The springs and streams of the mountain show 

 this by their volume and freshness, the creeks and rivers, 

 in the cultivated portion, drying up in the summer months. 

 The constant prevalence of the regular air-currents, always 

 of some degree of intensity, from gentle breezes to rush- 

 ing streams, carry off to the northeast most of the mois- 

 ture which they drink up from the surface of the moun- 

 tain. This occurs almost constantly, except during the 

 prevalence of regular storms of precipitation, or local cloud- 

 falls. The meeting streams from the northeast, running 

 as under-currents in a direction opposite to the regular 

 marching of the storm, then, of course, drop their local 

 additions or feedings from local evaporation. In fact, the 

 air-currents, from far distant spaces of the air-ocean, are the 

 regular water-carriers of the Alleghany Mountains ; while 

 constantly prevalent winds, or gentle air-streams take up the 

 moisture of the surfaces, to be precipitated in distant spaces 

 of the earth or ocean of water again. The presence of any 

 undue humidity in the atmosphere of the mountain heights 

 is proved, moreover, by recorded observation, not to exist. 



From this whole condition of things it follows that the 

 exact hygrometric range of the mountain's atmosphere is 

 nearly the same as at corresponding latitudinal points at its 

 base below, with the unexpected difference only that the air 

 is dryer ; leaving to be explained by the local influence 

 already described of large forests in a state of nature, re- 

 ceiving and retaining in their cool shades the water sup- 

 plied by the clouds, uninfluenced by the evaporating power 

 of the sun and winds coming in contact with the earth's 



