6 AUSTRALIAN WEATIIKK. 



It i-> diHicult to understand how an anticyclone can, to all 

 intents and purposes, stand still for several days when the whole 

 surrounding atmosphere is moving forward ; and we have not yet 

 made out the explanation. But facts, and some very significant 

 ones, are accumulating which indicate the probable explanation. 

 For instance, when such a stoppage occurs, the isobars in front 

 widen out, showing that the preceding system is moving forward ; 

 and the closing up of the isobars in the rear shows that the 

 following one is coming forward. We know also, as already 

 pointed out, that the source of pressure, the descending current in 

 the anticyclone, may, and does, vary in locality from day to day 

 with regard to the outlying isobars, coming down at one time on 

 the preceding side of the centre and at the next on the following 

 side. This gives an oscillating position to the apparent centre. 

 But it seems impossible that a mass of air, even that in one anti- 

 cyclone, without reference to its surroundings, measuring as it 

 does '2,000 miles by 1,000 miles, can be actually stopped in its 

 forward motion. This point is however, one of those still under 

 investigation, and we hope in another paper to make the explan- 

 ation complete. 



In America it is well known that cyclones move ten to fifteen 

 per cent, faster than anticyclones, but there the low pressure 

 acquires a velocity of its own in addition to that which it has in 

 common with the general mass. The conditions here, as already 

 pointed out, are different, the low pressure not being independent, 

 but tied to the anticyclone, as effect is to cause. 



Another point of considerable importance is the normal latitude 

 of the anticyclones in each month of the year. At times it is a 

 very uncertain matter, for there is as much difference in the 

 latitudes of tracks in the same month in some cases as there is in 

 the average tracks for each month of the year. Still, taking the 

 four and a half years of available records, there is a very obvious 

 monthly change of latitude, which is best indicated in tabular 

 form. 



