522 J. w. BEWS. 



The cold air, which thus flows down to lower altitudes, has 

 to be replaced by air from above, which has not been cooled 

 by radiation and is further warmed by compression as it 

 descends. Consequently, the air on the mountain sides and 

 even at the top may be relatively wai'm in winter. At the 

 same time it is very dry. The valleys, therefore, are damp 

 and cold at nig'hts, the mountains dry and warm. 



On the other hand, during the day-time, and particularly 

 during summer, the temperature of valleys is relatively high, 

 owing to the heat resulting from insolation being reflected and 

 radiated from the sides of the valleys. The foot of the main 

 escarpment, for the same reason, is relatively Avarm. The 

 valleys and lower altitudes generally, therefore, show a much 

 greater range of temperature than the enclosing mountains. 

 A decrease of the annual and diurnal range of temperatures 

 is a general feature of high altitudes, but it depends to a 

 large extent on the topography. A valley at high altitude 

 will show a much greater range than a hill of the same 

 altitude. 



A common feature of mountain ranges in higher latitudes, 

 where there is a covering of snow, is the retardation of the 

 time of occurrence of maxima and minima temperatures and 

 of the seasons generally. This does not apply to the Drakens- 

 berg. It is true that snow may lie on the summit for several 

 weeks, but its melting does not require a very large amount 

 of insolation, and so it does not lead to any postponing of the 

 advent of summer. On the contrary, the melting snow 

 supplies the necessary moisture to give the vegetation an 

 early start, and as a matter of fact the mountain regions 

 of Natal have an earlier spring tlian the Midlands. It must 

 be remembered that in Natal the rest during the winter 

 season is due to drought rather than cold. 



No exact meteorological figures have ever been taken for 

 the higher parts of the Drakensberg, but the following table 

 gives the average for three years, 1902-1904, for Qudeni, 

 5686 feet (1734 m.), and Weenen, the valley type, alt. 

 2841 feet (866 m.) : 



