90 The N.Z. Journal of Science and Technology. [Mar. 
An anticyclone, as its name suggests, is the reverse of a cyclone, for the 
pressure is highest in the centre, and gradually diminishes outwards. The 
winds are more variable, particularly in the central region, while in the 
Southern Hemisphere their general direction is opposite to the motion 
of the hands of a clock, the front of the centre, when it is moving due east, 
having southerly winds, and the rear northerly. The winds generally have 
but little force, since the isobars are not so closely bunched together as in a 
cyclone. 
The most important conditions relating to these two systems are the 
association of unsettled weather with cyclones, or low barometric pressure, 
and fair weather with anticyclones, or high barometric pressure. 
Areas of high and low pressure entirely control our weather, and the 
changes due to both are brought about by their translation across the 
Dominion, for the whole system of isobars moves forward from west to 
east, and when any distinct type in the system is passing over the country 
the winds and weather usually associated with such a type are experienced. 
Our knowledge of the direction and rate of their movements makes the 
forecasting of weather possible. 
Circumpolar Pressures. 
There are two theories with regard to the arrangement of the Antarctic 
circumpolar system of isobars. The one which seems the more likely in the 
light of the observations made by explorers in recent years is attributed to 
Lockyer, and is as follows : The polar region is covered by relatively high 
pressure, while on its outer or northern perimeter are a succession of cyclones, 
which are constantly travelling from west to east at the rate of about 
400 miles per day. Such a distribution of pressure would account for the 
strong westerly winds between the 40th and 50th degrees of latitude ; from 
the 50th to the 60th we then expect to find easterly and southerly winds, 
and beyond the 70th degree there would be a continual outflowing of 
southerly winds from the Pole. 
The other theory is that the whole of the polar area is covered by an 
immense cyclone which is centred at the Pole. If this were correct we should 
invariably expect westerly winds in the higher latitudes ; but Sir Douglas 
Mawson at Adelie Land experienced mostly southerly and south-easterly 
gales. The lowest pressure, also, would nearly always be found nearer the 
polar region ; but according to both Sir Douglas Mawson’s and Captain 
Amundsen’s observations this is not so, for pressure is invariably lowest 
farther north. 
The Macquarie Island* reports have been extremely valuable in helping 
to elucidate this matter, and from these it would seem that the centres of 
the cyclones above referred to pass usually somewhat to the south of that 
island. 
The mean number of intense “ lows ” passing Macquarie Island during 
the three years 1913 to 1915 was as follows : January, 6-3; February, 5-7 ; 
March, 3-6 ; April, 4-0 ; May, 5*0 ; June, 4-3 ; July, 5-7 ; August, 4*3 ; 
September, 6-0 ; October, 9-3 . November, 6-5 ; December, 4-0. 
There are therefore sixty-four cyclones pas ing during the year, and, 
taking the average rate at 400 miles per day, there would appear to be at 
least eight or nine primary cyclones circling the subantarctic regions at the 
same time. 
* The Macquarie Island wireless station was established in connection with Sir 
Douglas Mawson’s Australian Antarctic Expedition. It was closed down about the 
beginning of December, 1915. Discussing the matter publicly at the time, Mr. D. C. 
Bates, Director of the Dominion Meteorological Office, said, “ It is a distinct loss to 
science. . . . The importance of Macquarie Island is very great, since it is so far 
south and yet has relationships so closely affecting our conditions.” 
