140 HENRY A. HUNT. 



occasion it went far beyond this and registered the unprecedented 

 velocity of one hundred and fifty-three miles in the hour in a gust. 



ONLY FORTY MILES PER HOUR. 



Now the southerly burster seldom exceeds fifty miles, and 

 generally ranges between twenty and forty miles per hour. 

 Whether this result arises from the fact that civilisation has raised 

 much brick and mortar to obstruct the atmospheric disturbance, 

 or whether it is that the absorption or radiation of heat is less 

 from the cultivated soil than from the hard, unbroken surface of 

 the pre-cultivation days, is a matter of conjecture only. 



BURSTER ANTECEDENTS. 



The climatic conditions preceding a southerly burster are, first, 

 a period of high temperature varying from three hours to three 

 or more days, accompanied in the early part of the summer, or 

 towards its close, by wind from the west or north-west, and 

 in the midsummer months, generally from the north-east. In 

 the early morning on the day of a "burst" the sky is white 

 and hazy of aspect. As the hour of the outbreak approaches 

 there begin to accumulate in the south, ball-shaped cirro-cumulus 

 or pilot clouds, and frequently, if electric disturbances are to 

 accompany the squalls, heavy cumuli thunder-clouds rise gradually 

 in the south-west. 



THE CLOUD ROLL. 



An hour or so before the squall, a heavy cumulus roll appears 

 low down on the southern horizon — the interval between this 

 apparition and the beginning of the gusts depends entirely on the 

 velocity of the wind. Afar off this cloud roll appears most 

 frequently due south, but sometimes south-south-west, or even 

 south-west ; it is sharply defined, dark on the edges with lighter 

 shades towards the centre. The roll is from thirty to sixty miles 

 in length. Sometimes it appears singly ; on other occasions there 

 are a multitude of these formations heaped one above the other, 

 with light cirrus below. Generally, if the burst is of the first 

 order, it is followed by an overcast sky composed of nimbus from 

 which patchy rain descends. (See Plate 8.) 



