Besults of further Experiments on Table Mountain. 99 



only, which corresponds, roughly speaking, to 8 m. per sec. As 

 there are 3,600 seconds in an hour, a velocity of 8 m. per sec. means 

 that during one hour 28,800 cub. m. of air would pass successively 

 over the same surface of 1 square m. ; and as each cubic metre 

 of air is carrying 1*68 grammes of suspended water, the total quantity 

 of it passing this area would be 48,384 grammes, a quantity which, 

 if deposited on an horizontal surface of 1 square m., would be 

 equal to 48 mm. of rain, or, in round figures, c 2 inches per hour. 



That is taking into consideration only a layer of air 1 m. thick ; 

 but the cloud is often 100 or more metres thick, and as the masses 

 of cloud in their course over the mountain are hurled and whirled 

 about, any portion of the lower layer, that may have been deprived of 

 its suspended moisture by the reeds, is constantly mixed with fresh 

 masses from above, and there is evidently much more moisture 

 available than many miles of reeds * could ever capture. 



It is this large excess of condensed moisture which floats about in 

 the cloud in the form of small drops that accounts for the surprisingly 

 large deposit of water on the reeds and rocks and all other obstacles 

 in their way. Not all clouds possess such a soaking effect. I have 

 sometimes spent many hours on the mountain in thick clouds with- 

 out finding any moisture on the bushes or any water in my gauges. 

 That is specially the case during northerly winds ; but when a real 

 south-easter blows things are quite different, and I am sure it would 

 simplify the discussion considerably, if some of the sceptics would 

 give me the pleasure of their company on such an occasion. 



Such a cloud is really an intimate mixture of an ordinary cloud 

 with a very finely distributed rain in its initial stages, and as this 

 mass is moving with great velocity, the minute raindrops are not 

 allowed to fall, and are captured only when they come into contact 

 with a solid body. 



Another objection against the method employed, and the con- 

 clusions drawn from the observations, has been laid before this 

 Society by Mr. Charles Stewart,! in a paper read in July, 1903, and 

 entitled "A Note on the Quantities given in Dr. Marloth's Paper 

 on the Moisture Deposited from the South-east Clouds." Mr. 

 Stewart took considerable pains to calculate the total surface of the 

 vertical superstructure employed by me, and found that the vertical 

 " catchment area " of the gauge, i.e., the surface of the framework, 

 reeds, and other parts amounted to 114 square inches, which is six 

 times as much as the horizontal area of the gauge. I am much 



* I repeat the explanation on p. 404 of my previous paper, that these plants are 

 not real reeds, but resemble them only, belonging to the order Restionacea. 

 f Charles M. Stewart, B.Sc, Trans. S.A. Phil. Soc, vol. xlv., p. 413, 1903. 



