THE TRAIN SACTIONS 



OF THE 



SOUTH AFEICAI PHILOSOPEICAL SOCIETY. 



THE WINTER STORMS OF SOUTH AFRICA, ILLUS- 

 TRATING THE VALUE OF CAPE POINT AS A. 

 WARNING STATION. 



BY 



[RE4.D 28th September, 1886.] 



On entering into the question of the meteorology of Cape Pointy, 

 it is intended to show how an isolated peak of medium altitude, inter- 

 cepting the path of a cyclone, may be utilized as a warning station, 

 to places further to the west and in its immediate vicinity. 



Before discussing this question, it will be necessary to glance at- 

 the atmospheric currents of the earth generally. Roughly speaking,. 

 the earth can be divided into a series of zones of which the following, 

 is the genera] summary : 



An equatorial zone of cahns. Two trade wind zones. Two semi- 

 tropical zones of calms, and two return wind zones. This is the 

 general geography of the winds of our globe, the only portion whichi 

 will affect us to-night being the trade and semi-tropical zones of the 

 southern hemisphere, more particularly applying to South Africa. 



About the latitude of Cape Town is situated that high pressure-, 

 belt from which the south-east trade winds blow : this south-east 

 trade current carries the atmosphere to the equatorial region of calms,, 

 where it rises and flows back again as an upper north-west current,. . 

 bearing the name of the upper return trade wind. 



The altitude of this current must be very great indeed near the 

 region of calms, for Smythe when at Teneriffe at a height of 12,000 

 feet above sea level, was still in the region of calms dividing the two^ 



