The Barometer in South Africa. 



85 



In these diagrams all pressures are reduced to sea-level, except that in 

 the ist and 2nd diagrams a constant reduction has been used for 

 Johannesburg so as to bring the curve amongst the others. It will 

 be noticed in the ist diagram that there is a great similarity between 

 the curves for Durban and Johannesburg, but that the curve for the 

 Cape is displaced. In the 2nd diagram, the Cape curve is advanced 

 36 hours and compared with the Johannesburg curve. It is at once 

 seen that the two curves now fit much better. The irregularities about 

 the 31 May- 1 June will be referred to further on. Collectively these 

 diagrams show that the movements of the barometer at the Cape 

 precede by 24 to 48 hours similar movements at Johannesburg and 

 Durban. This is a fact of fundamental importance because, as just 

 stated, it will permit us to forecast the weather. In Europe and 

 North America the weather is governed by the advance, roughly from 

 W to E, of closed areas of low barometer readings called cyclones, 

 and analogy would predict that cyclones should also rule our weather 

 in South Africa. Australian experience, however, warns us that this 

 may not be so. Russell and Ellery both state that cyclones only play 

 an insignificant part in Australian Meteorology, and that the weather 

 there is governed by a procession, from W to E, of anticyclones or 

 closed areas of high barometer readings, in between which are V 

 shaped depressions which bring stormy weather. The excellent 

 weather maps published by the Argentine Meteorological Office 

 confirm the Australian experience. A continuous procession of 

 cyclones is passing over S. America south of 40 S.Lat., whilst a 

 continuous procession of anticyclones is found north of 35 N.Lat. 

 This diagram made from 3 days' maps shows the usual routine. 



Argentine, 1st Ai^ril, 1906. 



