54 Report S.A.A. Advancement of Science. 



currents help us in the following way. If the core leaves the ocean 

 there will be no centre for the winds to blow round. The currents, 

 which are the direct result of the persistent winds belonging to these 

 permanent systems, will slacken if the core remains away a sufficient 

 time, and the charts will record a change in velocity. If the system 

 is far from its mean position w^e have no difficulty in believing such 

 reports as we are hearing now, that a current like the Gulf Stream is 

 changing its course. Reliable indications of the mean positions of the 

 cores of the Atlantic anti-cyclonic systems in both hemispheres are 

 given by the monthly charts of the ocean currents. There is no neces- 

 sity, in order to understand the charts, to go beyond what these mighty 

 weather controls — the permanent anti-cyclonic systems of the globe — 

 tell us. In this connection I would bring to your notice the reversal of 

 the Agulhas current, close in-shore along the south coast of Africa, 

 which appears in these charts in certain winter months. As far as my 

 investigation has at present gone, this fact is at once the proof that 

 an anti-cyclone system prevails over South Africa during the months 

 wdien the reversal takes place, and an indication of the position which 

 that system occupies. I would urge upon the Observatories of Cape 

 Town and Durban to give their attention to this point, for if the 

 connection between the two facts can be established, it would enable 

 warnings to be issued beforehand, which may be the means of saving 

 many a ship. Only recently there w^as a wreck which w^as held to 

 be due to abnormal currents along the south coast. 



Progressive Movements. 



In the absence of daily synoptic charts to help in tracing the 

 progressive movements of anti-cyclones, we must turn to all the data 

 that have been collected regarding winds, rainfall, temperature, 

 pressure, cloudiness, and humidity. 



That there has been some change in the distribution of pressure 

 over South Africa in recent years is shown by the continued drought 

 which has prevailed over some parts, especially the Transvaal and 

 the Orange River Colony. Moreover, we have in Mr. C. M. 

 Stewart's important paper on South African Meteorology, contributed 

 to the Association in 1903, strong proof of the same fact. He 

 pointed out that an investigation of the tri-daily observations made 

 at the Royal Observatory during the period 1896-1900 led him to very 

 different conclusions respecting the prevalent winds, from those given 

 by Dr. Buchan in the Challenger Re fort for the 18 years 1842-55, 

 1862-65. 



A comparison of the two tables, month by month, in which the 

 percentage frequency of the winds from the 8 principal points of the 

 compass is given, indicates that whereas the Challenger results make 

 the South to be the prevailing direction of the wind in every month of 

 the year, Stewart's analysis shows decided traces of a " monsoon " 

 influence ; in that during the winter months, June-August, the 

 prevailing direction is north-westerly, while during the rest of the 

 vear it is southerlv. Both tables indicate (i) that in every month the 



