xxii Prorpp(]iiu/s of Iho SoiitJi African PMlosophiccd Socirtjj. 



rain or cold, cloudy weather. The barometer falls during a Berg- 

 wind and rises after. 



The description given by the various observers leaves no doubt 

 that the E. wind of Port Nolloth and the Berg- winds of the south 

 coast belong to the same category as the Fohn of Switzerland, the 

 Chinook of Canada and the United States, and the North-Westers of 

 New Zealand, from all of which, however, they differ in the absence 

 of a cloud mass on the mountains, owing to the air coming from the 

 dry interior of top of Africa. 



The Port Nolloth E. winds may be accounted for by the 

 formation of a cyclone in the South Atlantic, having its centre to 

 the N.W. of Port Nolloth, and travelling in a S.E.'ly direction, while 

 the interior of Africa is probably occupied by an anti-cyclone. The 

 centre of these cyclones evidently passes to the north, and sometimes 

 to the south of O'okiep, similarly to those of Clanwilliam. In the 

 case of Storms Eiver, the centre of the cyclone probably lies S.W. of 

 this station and travels westwards. 



The explanation of the conversion of a cold wind into a hot wind 

 was given by Dr. Hann, of Vienna, in his investigation of the Fohn. 

 The air w4iich is drawn away from the base of the mountain towards 

 the centre of the cyclone is replaced by the air from the plateau, which, 

 being pressed upon in its descent by other air rolling down on top of 

 it, is compressed to a slightly greater density, and heated approxi- 

 mately at the rate of 1-6° Fahr., for every 300 feet of descent (called 

 the " normal adiabatic rate "). 



The Cape Town South-Easter more closely resembles the Fohn in 

 having occasionally cloudy mass forming the well-known " Table 

 Cloth " of Table Mountain. 



It is proposed that the general term " Berg-w^inds " would 

 sufliciently indicate the nature of such winds in Cape Colony, 

 where, from its physical configuration, such winds should be of 

 common occurrence. 



The rise in the barometer before these winds at O'okiep and 

 Clanwilliam points to the probable existence of a peri-cyclonic 

 ring of high pressure, separating the cyclonic circulation to 

 westwards, from the probable anti-cyclonic circulation of the 

 interior. 



Mr. D. HuTCHiNS stated that he had had a large experience 

 of Berg-winds, and could say that often the ordinary wind 

 of the Karoo became a Berg-wind undei; tlie mountains. There 

 was no doul)t in his mind that Mr. Stewart was right in his 

 explanation. 



