58 



Report S.A.A. Advancement of Science. 



In the chart for May (Appendix II.) we see that high pressure 

 is firmly established over the Transvaal, and that the centre is lying 

 upon Lat. 27° S. From the distribution of pressure it is evident that 

 the centre is already to the east of the Colony, and that it has merged 

 wiih the Australian system coming from the east. We can further 

 test this point by examining the barometer readings at the various 

 Transvaal stations for the first 6 months of 1905, as given in the 

 recently-published second annual report of the Transvaal Meteoro- 

 logical Department. Taking the stations from west to east we have 

 the following monthly means : — 



BAROMETER READINGS— MONTHLY MEANS. 



All these records attest the same fact, whether they are made at 

 stations in the North, South, East, or West of the Colony, viz., that 

 high pressure arrived in 1905, in the month of April, and that the 

 barometer fell as it passed on. The pressure is highest in that 

 month at every station in the Transvaal. 



Now let us turn to the Australian Anti-cyclone, and see what 

 progressive movements can be traced from the information that is 

 available. The records of the Royal Alfred Observatory, Mauritius, 

 give us what we require. It is in Lat. 20° 5 S. and Long. 571° E. 

 It is somewhat north of the normal track of the Australian system, but 

 the records bear the unmistakable traces of its influence, as it passes 

 westwards and returns eastward during each year. In the Report for 

 1900 the following mean monthly barometer readings are given for 26 

 years : — 



BAROMETER READINGS. 



Jan. Feb. Mar. April 



29751 -734 -769 -818 



Aug. Sept. Oct. Nov. Dec. 



30-010 29-998 -939 -878 -814 



Monthly Means. 

 26 years. 



July 

 30-008 



May 

 -888 



June 

 -964 



The minimum occurs in February, which we have already found to 

 be the month when the anti-cyclone is in its extreme summer position 

 near Australia, and consequently furthest from Mauritius. It then 



