404 Transactions of the South African Philosophical Society. 



at its vegetation, that the south-western corner of the Cape has a 

 dry and practically rainless summer, for the hills and lower slopes 

 of the mountains from Cape Town to Clanwilliam, and from Caledon 

 to Worcester and Ceres, are covered with dull-coloured, highly 

 xerophilous shrubs and shrublets. Quite a different aspect, however, 

 is presented by the higher mountains. Wherever one ascends them 

 one finds that even in summer the vegetation of the higher parts is 

 much denser than that of the slopes below. While on Signal Hill 

 or the Paarlberg, at Caledon or at Tulbagh, a good deal of bare 

 ground is visible between the shrubs, the higher mountains are 

 covered with a thick layer of closely set vegetation. Every crack 

 and crevice, every little depression, every ledge is occupied, and even 

 precipitous walls are often clad with a luxuriant mass of shrublets, 

 reeds and rushes. 



Having visited many of the mountains of this area, and having 

 spent many a day on their lofty heights, I felt more and more con- 

 vinced that the vegetation of these higher regions could not exist 

 without a regular supply of moisture, and that it consequently could 

 not depend on the rainfall only for its water supply, but that the 

 clouds, which cover these mountains during the south-east winds, 

 must provide them with an additional and not inconsiderable 

 quantity. 



That there is no lack of such moisture in a south-east cloud is 

 easily realised by any one who has ever spent a couple of hours in 

 it. Grass and bushes may have been perfectly dry while the 

 weather was fine, yet a few minutes after the formation of the table- 

 cloth every leaf and every reed is covered with drops of water, and 

 if the wanderer has to force his way through these reeds and 

 rushes," he will soon be as wet as if he had been out in a drizzling 

 rain for a couple of hours. 



For years it had been my wish to obtain some definite figures 

 concerning the amount of water condensed from clouds in 

 this way, but it appears that no such experiments have been 

 conducted either here or anywhere else ; at least, I could not 

 find any records in handbooks on meteorology. It became, there- 

 fore, necessary for me to endeavour to obtain this information 

 myself. 



In November, 1901, I took two 5-inch rain gauges to the top of 

 Table Mountain, and placed them about midway between the east 



* The designation reeds and rushes is not correct in a botanical sense. The 

 plants resemble them only in their appearance, but they belong to another order, 

 viz., Rcstioiiacece. 



