34 AUSTRALIAN WEATHER. 



does so it is usually the result of a cyclonic disturbance on the 

 north coast, such as existed, for example, in the " Dandenong " 

 burster, the effects of which were felt considerably north of 

 Brisbane. The northern boundary of the burster may be defined, 

 as limited by the south-east trade winds, which blow almost 

 incessantly north from about 30 S. latitude. Other areas of 

 actual experiences are given on page 40. 



CHANGE OP TEMPERATURE. 



Bursters always result in a diurnal drop in temperature, the 

 said drop ranging between 37'5 and 4'2 with an average fall of 

 18-1. The greatest diminution of temperature takes place during 

 the first hour, and the fall is most sudden when the burst comes 

 at midday. The steepest drop on record was that registered at 

 1'50 p.m. on the 30th December, 1891. The maximum then read 

 ; five minutes after the change to south it read 80'3, being 

 a difference of 17 '2 ; two minutes later there was a fall to 7 9 -7 

 or a further difference of 0'6. The thermometer remained at 

 this reading until after two o'clock, but at 2-15 it descended to 

 75, being a drop of 4'7 more and a total drop of 22'5 in twenty- 

 five minutes. The diurnal range in this instance was 23 '8. 



VELOCITY OF WIND IN THE BURSTER. 



It occasionally, though rarely, happens that the greatest velocity 

 of a burster is reached at the change or during the first hour 

 thereafter. In most cases, however, the maximum force is attained 

 about twelve hours afterwards. As the majority of bursters occur 

 between the hours of seven and twelve p.m. (see Table I.), it there- 

 fore follows that the wind is usually strongest between seven and 

 twelve a.m. on the following day. 



UNSEASONABLE WINDS. 



In these instances where the greatest velocity was reached im- 

 mediately on the arrival of the burster, the winds preceding were 

 generally of an unseasonable character that is to say north- 

 westerly in the summer and north-easterly in the spring and 



