2 AUSTRALIAN WEATHER. 



The fixed anticyclone over the Indian Ocean in these latitudes, 

 which is found in books of reference, must give place to a moving 

 series. It is not difficult, now that the true weather conditions 

 are known, to trace the development of the idea of a fixed 

 juitu-yclone over this part of the ocean. The moving anticyclones 

 are about five times as large in area as the low pressure A 

 between them, and they are also moving to the east at the rate 

 of about 400 miles per day. Now vessels crossing these at 

 random would necessarily find five times as much high pressure 

 as low pressure : and if travelling with the anticyclone would 

 keep in it for many days, perhaps all the way from the Cape to 

 Sydney, as the Havanah did. When all these barometer readings 

 came to be plotted on the chart the result would be a fixed anti- 

 cyclone, which we now know has no existence in fact. It is not 

 so easy to trace the history of the " overland " fixed anticyclone 

 of more modern writers, but it is equally imaginary. The high 

 pressures regularly move on over land as well as over ocean. 



It will perhaps be more convenient if I state here, in as few 

 words as possible, some of the results obtained, and bring forward 

 subsequently in more detail the data upon which they are based. 

 These results may be briefly stated as follows : 



1. Instead of fixed anticyclones we have a series of moving ones. 



2. The average number of anticyclones passing over Australia 

 in a year is forty-two, and so far as the observations go, the 

 number varies but little. See Table I. (p. 5). 



3. Anticyclones are more numerous in summer than in winter. 

 See Table I., and diagrams 9 to 20. 



4. The latitude of anticyclone tracks varies with the season, 

 being in latitude 37 to 38 in summer, and 29 to 32 in winter. 

 See Table II. (p. 7). 



5. Upon the average, an anticyclone travels across Australia 

 in seven days in summer, and in nine days in winter. Since 

 forty-two pass over each year, the average time of passage over 

 any place is 8*7 days. 



