XIV 



Transactions of the South African Philosophical Society. 



Winter depressions are larger and more pronounced than those 

 of summer ; but at no time are the ordinary diurnal curves 

 obliterated, although they are modified in a very interesting way 

 by barometric disturbances. The average maximum deviation of 

 pressure from the mean, in the 105 cases made use of, is just 

 about one- seventh of an inch. Directly in front of the trough of 

 a depression the temperature averages 2° higher than usual ; there 

 is a slight increase of the vapour contents of the air, and of the 

 clouds. In the immediate neighbourhood of the trough the velocity 

 of the wind increases considerably ; also the rain-frequency and 

 intensity are both greatly augmented. In the rear of the depression 

 it is colder and drier, and the wind, though strong, is steadier and 

 less dusty. The paper shows that the variations in the velocity 

 of the wind may be partly explained as a combination of the normal 

 winds with the cyclonic winds of the depression. 



The curve showing the variation of the resultant wind-direction 

 during the passage of a depression is of much interest. It seems 

 that the east component is very little affected, and that the departure 

 from the mean falls almost entirely upon the north component. 

 Taken in conjunction with the fact that the east component curve 

 is essentially a curve of temperature, this result is important. 

 Another result is that the extremity of the direction-resultant veers 

 at all times in conformity with the normal curve. The prevailing 

 direction of motion of these depressions is from south-west to 

 north-east across the central tableland, and they reach Kimberley 

 and Durban some twenty to forty hours after passing over Cape 

 Town. 



Ordinary Monthly Meeting. 

 June 28, 1905. 

 Dr. J. D. R Gilchrist, President, in the Chair. 



The following nominations were made : Messrs. J. G. Caink, 

 Cape Town, by E. H. L. Schwarz and A. L. du Toit ; J. ffolliott 

 Darling, Bulawayo, by W. L. Sclater and L. Peringuey; J. 

 Jeppe, Cape Town, by E. Marloth and L. Peringuey. 



Messrs. H. S. Harger, Dr. G. Potts, J. S. Backhouse, F. 

 Pickering, and Dr. E. C. Long were elected ordinary members 

 of the Society. 



Mr. W. L. Sclater exhibited the remains of the boundary beacon 

 erected on the Zeekoe Eiver, in what is now the Colesberg District, 

 in the year 1778, by the Governor, Joachim van Plettenberg. The 

 remains of the stone bearing the arms, date, and part of the name of 



