162 ON AUSTRALIAN STORMS, 



ing danger. But it does not follow that the Adelaide reports 

 are sufficient for this purpose. It is said by some persons that 

 the prevailing gales of these Colonies originate in the Southern 

 Indian Ocean, and pass over Adelaide before reaching us. Al- 

 though this may be true in the majority of cases, it will sometimes 

 happen that our east coasts are subject to gales from which 

 Adelaide either wholly or in part escapes. Admiral Fitzroy has 

 shown that a polar current advancing from the north towards 

 the British Isles, is sometimes carried so far eastward by the 

 general movement of the atmosphere as to pass between Norway 

 and the east coast of Scotland, spreading itself over the North 

 Sea, and there encountering the tropical current from the south- 

 west ; both being deflected westward by Danish and Dutch 

 shores, and combined producing those violent easterly gales 

 which are so destructive to the shipping along the east coast of 

 Great Britain. Such easterly gales are not first felt at the 

 meteorological stations in Ireland and the west of England. The 

 approach of the two great currents would be first announced 

 from the north of Scotland and from the French coasts. 

 Instances analagous to this occur in these Colonies. Let us 

 suppose an area of diminished pressure with northerly winds to 

 be passing over Adelaide eastward, and a powerful current to be 

 advancing from the south-east towards this point. Before the 

 extremity of this current can reach Adelaide it is carried east- 

 ward by the general circulation, and so passes over Tasmania 

 along our eastern coast, meeting, probably, the warm moist 

 current from the north, and so producing one of those terrific 

 easterly gales which are so remarkable for their down-pour of 

 rain. In such a case as this we must not trust to Adelaide alone 

 for warning ; the reports from that station must be supplemented 

 by those from the Tasmanian coasts. We have before us a very 

 striking exemplification of the case I have just mentioned. If 

 we examine the curves at the close of April, we shall find what 

 appears at first view an exception to the theory of eastward 

 circulation, namely the barometric minima at Sydney and 

 Brisbane precede those at Adelaide and Deniliquin. At Adelaide 

 northerly winds were remarkably prevalent with high temper- 

 ature throughout the 27th, 28th, 29th, and 30th April and 1st 



