SOUTHERLY BURSTERS. 57 



It is necessary to state here that in the conditions under which 

 this prize essay was written, there is no express definition of the 

 minimum velocity of wind which shall constitute a burster, I have 

 therefore taken as such every sudden shift of wind to south or 

 south-west, from any point between west and north on the one 

 side and east and north on the other side, irrespective of the 

 velocity of the wind ; always provided however, that the velocity 

 was maintained subsequently for some hours with force. 



It will be observed that the table brings to light the fact, that 

 the mean velocity of the wind is greater in spring than in autumn, 

 which may be accounted for by the fact that our September 

 equinox is windy and the March one wet. The discrepancy 

 between the seasonal total in the tables is accounted for by the 

 fact that the anemometer on a few occasions failed to record the 

 hours of arrival, in these cases the burster is omitted from Table I. 



One other point sfeems important in respect to the arrival of 

 bursters, and that is the time between the lowest barometer and 

 the arrival of the burst. 



DIAGRAM III. 



Gives the fluctuations of the self recording barograph for twelve 

 hours before and after nineteen bursters of the summer 1893 to 

 1894. The curves have been drawn with their lowest points in 

 a vertical line, and the times at which the burst commenced on 

 each curve have been connected by lines, thus showing the rela- 

 tion between the barometic minimum and the time that the 

 burst of wind reached Sydney. It will at once be seen that the 

 bursters occur some hours after the barometers have commenced to 

 rise, and if this set of curves be accepted as the general rule, the 

 diagram shows that in any season the lowest readings take place 

 more remotely from the change of wind, early in the summer. It 

 is also patent that no particular height of barometer is peculiar to 

 the burster. A sudden rise does not indicate that the blow will 

 be a hard one, see the sharpest that of 17th September and of 

 30th November, while the velocity of forty-eight miles per hour, 



