'I'HR VEdKTATlON OF NATAL. 273 



level, but after that is passed a sudden chill is felt. The cold 

 continues until one ascends to the same level on the opposite 

 side. Looking back, a white mist-cloud can be seen forming 

 in the valley — the cold winter mist already referred to. 



The cold uir flows downwards along the valley. The upper 

 end is usually warmer than the lower end. Where a small side 

 valley opens out into a larger and deeper one the cold ;iir 

 flows out of the former. As a consequence plants in the side 

 valley may be little affected by frosts. This doubtless 

 explains why in the Chase Valley near Pietermaritzburg it 

 is found possible to grow certain of the sub-tropical fruits. 

 The Dorp Spruit, which is at a lower level, cuts across the 

 end of Chase Valley and drains off the cold mist. In the 

 same way it is found that plants at the upper end of a valley 

 suffer less from frosts than those at the lower end. 



4. Temperature of Bush. — The woodland areas are' like the 

 coast-belt in having less variation in temperature. The great 

 amount of transpiration from the extensive leaf-surface has 

 the effect of lowering the temperature during the day. 

 Further, thei-e is less rapid cooling during the night. Frosts 

 are rare inside the bush. This fact is of very great import- 

 ance, for, though the winter is dry, the trees liave not at the 

 same time to grow in a frozen soil, and consequently very 

 few deciduous trees occur. 



5. Temperature Records. — The tables for temperature 

 illustrate in a general way the above-mentioned points. On 

 the first terrace (coast-belt) the temperature is only once 

 shown to have fallen below freezing-point — at Stanger in 

 1893. There is less range of temperature shown on the coast- 

 belt, though occasionally very high shade temperatures are 

 recorded, the highest being 116° F. for Stanger in 1901. 



The places have again been arranged according to the 

 terraces and the usual fall in temperature with rising altitude 

 is shown. From places on the second terrace and upwards 

 we get Avinter frosts. 



Attention should again be directed to Weenen and Qudeni, 

 since these places represent respectively the dry Thorn 



