.7320 J. jT. JiUfion: 



'that of the normal cvclones, that is, clockwise. Further observa- 

 tions, however, are required, as the records in this paper are too 

 few to come to a definite conclusion on the point raised,. 



A Gigantic Dust Whirl. 



Ihe whirl now to be described has been noted in the above list, 

 but its occurrence was so striking that a separate description 

 is warranted. 



This dust whirl was observed <m 19th February, 1917, at about 

 1.30 p.m., in the Comet Vale-Coongarrie district, when the sun 

 had not passed a great distance beyond the zenith. The day waa 

 hot and sultry, with a gentle north to north-west wind. The 

 -conditions w^ere, therefore, favourable for dust whirls. This par- 

 ticular whirl formed a great column of dust, the top of which 

 was above tAvo clouds, which were at different levels in the atmo- 

 sphere, the difference of level apparently being considerable. 

 These clouds were of the cumulus type, and Avere such as may be 

 -commonly observed in the area after midday under the conditions 

 mentioned. The dust column Avas broken by these two clouds. The 

 ■column was travelling southward, or south-westwards, at a 

 fairly rapid rate, but the rate of motion could not be deter- 

 mined, and in doing so, passed beyond the clouds, and showed 

 itself as one unbroken, gigantic column, Avith a pronounced bend 

 forAvard (i.e., in the direction of its linear movement) at the top. 

 Otherwise it appeared to be approximately vertical. The dust 

 AA'hirl Avas- close to the path of the sun's rays, and as the sun Avas 

 ■obscured by the upper cloud, the phenonema could be closely 

 Avatched. The dust Avas dull, red in colour, and betAveen the 

 tAVo clouds dense masses of dust could be seen by the naked eye 

 Avhirling about and springing upAvards. As it moved in the 

 direction mentioned, the column became invisible Avithin a fcAV 

 minutes. The direction of rotation could not be ascertained, nor 

 could any idea be formed of its diameter, although the diameter 

 appeared to be about the same through the Avhole length of the 

 column. 



The angle of elevation of the top of the column Avas guessed to 

 be about 80°, but the horizontal distance of the column from' the 

 point of observation could not be ascertained, so that it is impos- 

 sible to state its height, even very approximately. Judging by ob- 

 servation, it Avould certainly not be less than one mile distant, and 

 probably much more; but if it be assumed that the distance Avns 



