SOUTHERLY BURSTERS. 29 



continent, steady breezes throughout its circulating areas are the 

 rule during the six days it occupies in passing over the compara- 

 tively low lands of Australia, as it travels from west to east. 



ISOBARS FLATTENED BY MOUNTAINS. 



But when the anticyclone reaches the mountains of New South 

 Wales, the symmetry is disturbed by a flattening of the front 

 isobars against the mountains, which concurrently show a tendency 

 to spread northwards, aided probably, by the inclination of the 

 mountain chain towards the north east. 



INTENSIFICATION OF THE LOW PRESSURE BY MOUNTAINS. 



While this change is taking place in the high pressure, the 

 isobars of the \ depression in front of it are undergoing a similar 

 process. But as this depression is a much smaller system, the 

 front isobars are being squeezed against the highlands, while those 

 at the rear are also being compressed by the advancing high 

 pressure. The result is an acceleration of force in the northerly 

 and southerly winds which enclose the \ depression. When the 

 squeezing process has amassed sufficient energy to overcome the 

 obstruction, the gradients of the high pressure, in their efforts to 

 regain their normal condition, expand with great rapidity on the 

 eastern slopes and send the \ depression at a great rate to the 

 south-east. 



For the previous twenty-four hours the northerly currents have 

 been maintained by the \ depression, but when once the moun- 

 tains are passed the anti-cyclone takes up the running of the 

 southerly one. As a proof of this speaking particularly of the 

 central and northern parts of the coast the southerlies have 

 nearly always been found to circulate along the line of the sea- 

 board in the anticyclone isobars. After an anticyclone of this 

 character has entered by a three days' march into Australia, it is 

 very rarely indeed that its progress is checked ; but occasionally, 

 as the \ depression still travels on, it seems to drag the southern 

 side of the high pressure after it. At the same time, while the 

 body of the high pressure remains over Australia, the one preced- 



