SOUTHERLY BURSTERS. 53 



seen a well defined shower with rain drifting to north at an angle 

 of 45. (See Plate 4 taken at 7 p.m.) Above this well defined roll 

 cloud another fainter and less defined one is clearly but faintly 

 shown in the negative. The whole storm could be seen to great 

 advantage from the Observatory, and the roll came along getting 

 more and more defined, showing all the features just described 

 from 6'25 to 7 p.m., including the shower and the duplicate roll 

 above. At 7 p.m. it looked very close to us, and could not have 

 been more than three or four miles away, for five minutes later 

 the squall with a velocity of forty-two miles per hour and the rain 

 were upon us. On the photograph taken at 7 p.m., (reproduced 

 as Plate 4) the altitude of the lower edge measures 5, and taking 

 the distance to be four miles, the actual height above the ground 

 comes out one thousand eight hundred and thirty feet, and it 

 spread over at least 100 of the horizon, seventy of which the 

 photograph includes. The sun had set at 6 '38 p.m., and night 

 was closing in fast, hastened by the dark masses of cloud which 

 almost covered the sky. 



At 6-45 p.m., a long way off and due south, a thunder squall 

 was seen and no doubt marked the arrival of the burster there, 

 showing that the axis of the A was still inclined to south-south- 

 east as it was in the morning. The rate of motion of the axis of 

 the ,\ eastward to Sydney from its barometrically defined position 

 at 9 a.m., three hundred miles west of Sydney, to the Observatory 

 by 7 p.m. i.e., in ten hours, is seven hundred miles in the twenty- 

 four hours, or thirty-three miles per hour. 



In the original photograph delicate shading shows the rounded 

 cloud perfectly, with another delicate roll above it, but much of 

 the tine detail is lost in the reproduction. 



DANDENONG GALE. 



I have also added a diagram, (page 32) giving barometer and 

 anemometer conditions at Sydney during the famous Dandenong 

 gale, for comparison, the extensive and disastrous possibilities which 

 a burster may develop made this desirable. During this gale 



