AN ESSAY ON SOUTHERLY BURSTERS. 151 



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 y\ depression at a great rate to the 

 south-east. (See page 162.) 



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 anti-cyclonic isobars. After an anti-cyclone 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 y\ depression still travels on, it seems to drag the hee] of 

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

 of the high pressure remains over Australia, the one preceding 

 continues on its way towards New Zealand. This results in an 

 attenuated state of atmosphere on the northern coast of New 

 South Wales and on the shores of Southern Queensland. 



TROPICAL CYCLONES. 



If it so happens that one of the north-east cyclones is on a visit 

 to this region at the same time it is diverted from its customary 

 course — the track of these storms being generally to the eastward 

 of our coast — and avails itself of this partial void. Its irruption, 

 acting with the already existing \ depression, seems to result in 

 that peculiar class of storm, of which the Dandenong gale is a 

 notable example. 



Considering the intensity of this particular storm a few facts 

 concerning another of a similar character may not be considered 



