18 



can be traced over the ocean for more than three consecutive days ; and when such areas can be identified 

 for as many as three days, their movements are shown to be erratic and slow. 



Over the continents it is otherwise, and in connexion with an investigation, already referred to, the 

 writer found that from November to March inclusive the centres of moving anticyclones that appear over 

 Australia follow paths lying chiefly over the ocean, not far from but to the South of the island Continent, 

 thence over the Tasman Sea, and across or just South of the Middle and South Island of New Zealand ; 

 but from May to September inclusive, chiefly over the southern part of Australia, over the Tasman Sea 

 and New Zealand. 



He expressed the opinion that these anticyclones form over the cool plains of Western Australia during 

 the winter months, and over the relatively cool sea immediately South-west of the land during the summer, 

 spreading subsequently from the sea northward over the land. 



Evidence is not wanting, moreover, to prove that small areas of high pressure, breaking off the Indian 

 Ocean anticyclone, drift eastward and reinforce these high pressure areas that have formed ; and that the 

 relatively high-pressure ridges which follow in rear of depressions also are merged in these "highs." 



CHARTS OF MEAN PRESSURE AND AIR TEMPERATURE. 



By a close examination of the data exhibited on the charts of mean pressure for Noon G.M.T., month 

 by month, it is found possible to follow the seasonal oscillations of the tropical high-pressure belt, as 

 represented by the southern margins of the ocean anticyclones : and, by comparing each chart with the 

 Accompanying chart illustrating normal pressure distribution, to detect displacements of the belt from its 

 average southern limit in any month or series of months to which the charts refer. The evidence thus 

 afforded by the pressure charts is in a measure supplemented by a similar comparison of the charted 

 observations of air temperature with average results on the charts accompanying them. Thus it is found 

 that during the last three months of 1901 the southern margins of the South Atlantic, Indian Ocean, and 

 South-eastern Pacific permanent high-pressure areas were North and West of their average positions ; that 

 of the South-western Pacific was South of the average, and exhibited no departure from the average as 

 regards longitude. In these months the mean air temperature appears to have been above the normal in 

 the Atlantic and Indian Ocean divisions of the Southern Ocean ; but about the normal in the South-eastern 

 and South-western Pacific divisions. 



During the greater part of 1902 the ocean anticyclones were again North of their average southern 

 limits and the Atlantic anticyclone was West of its average position. The Indian Ocean and South Pacific 

 anticyclones, however, appear in their average positions as regards longitude. 



Air temperature over the Southern Ocean, as indicated by the charts, was in each month of this year 

 either about the normal or above it, except in the South-western Pacific division of the ocean, where it 

 seems to have been below the normal. 



During the year 1903 the southern margin of the high-pressure belt is charted in or near its average 

 parallels ; and, while the South Atlantic and Indian Ocean areas of maximum pressure are shown to have 

 been West of their average positions, the two South Pacific areas are located slightly to the East of the 

 average. 



As regards mean air temperature during that year, this appears from the position of the isotherms to 

 have been higher than the normal over the South Atlantic and the South-eastern Pacific divisions of the 

 Southern Ocean, slightly above the normal over the Indian Ocean division, and slightly below the normal 

 over the South-western Pacific division. 



In the first three months of 1904 the southern margin of the belt is charted in about its average 

 parallels. The air temperature indicated by the isotherms for those months is above normal, except in the 

 South-Western Pacific division, where a slight defect in temperature is indicated. 



In a paper contributed to the Royal Meteorological Society in 1908 by Colonel H. E. RAWSON, C.B., R.E.,* 

 it was pointed out that when isobaric charts of the Southern Hemisphere relating to any month or months 

 which had been prepared in different years were compared with one another, the action-centre of the South 



"The Auticyclonic Belt of the Southern Hemisphere," 'Quarterly Journal, Roy. Met. Soc.,' July, 1908. 



