THE VEGETATION OF NATAL. 289 



2o*62 in. were recorded, and at Verulam a record amount of 

 28 in. in thirty-three hours fell. Snow fell on the Drakens- 

 berg and over the border in the Transvaal. Extensive 

 flooding with much resulting- destruction, particularly in the 

 coast districts, was recorded. 



Hot winds in some cases appear to originate in a different 

 manner and to be somewhat local, although usually they 

 affect the greater part of Natal. I shall not attempt to enter 

 fully into the causes that are at work. They are similar in 

 some respects to the Foehn winds as described in the Rockv 

 Mountains by Prof. Davis. ^ The air at the lower level flows 

 out to supply an area of less pressure somewhere else, and 

 the air from above descends. Being warmed by compression 

 as it descends, it becomes a hot, dr}^ Avind. After a time it 

 rises again, and cooler moister air comes in, and then the 

 conditions return to what they were before the disturbance 

 began. 



(6) FIRE. 



This is a factor that is undoubtedly of great importance in 

 determining the distribution of woodland and grassland, as 

 well as affecting the character of both. 



Over practically the whole of Natal it is usual to burn the 

 grass once a year. The chief effects will be fully discussed in 

 connection with the separate plant formations. 



Fires appear never to originate in the bush except through 

 deliberate intention. It must, howevei-, be pointed out in 

 this place that the grass fires affect the bush by gradually 

 eating into the margins. 



(7) ANIMALS. 



1. Termites. — The termites or white ants have an important 

 effect both on soil and on vegetation directly. The commonest 



' Davis, ' Report on the Forest Conditions of the Rocky Mountains,' 

 Washington, 1889. 



