1854.] Report on the Dust Whirlwinds. 369 



<75~$""5~575~C"?5 > * on ly more circular than is here represented. 

 At the conclusion of the cyclone, slight rain fell, and as the storm, 

 passed away from the station, the atmosphere was left clear, except 

 towards the west, where the body of it was visible, progressing 

 onwards. 



From the above description of this storm several points of interest 

 are deducible, namely — 



a. The body of the storm consisted of a number of revolving 

 spiral columns of dust blown by the wind with a circular motion , 

 from L. to B,. and at the same time gyrating from the earth 

 upwards. 



b. The onward motion of the body of the storm was at the 

 station in a general direction from 1ST. E. towards W. but probably 



with more or less of a curve, or zig zag ''N/n' \/ ,y S/N^\ which 

 might account for the slight variations in the direction of the wind 

 during the observations. 



c. The convexity of the minor gyrating columns of dust being 

 always onwards, would indicate that the chief force of the storm was 

 at an inconsiderable height above the surface of the earth. 



12. — 9th April, 1853. Although the gusts of wind and dust 

 which occurred during the day cannot properly be included as 

 "storms," they nevertheless presented a few peculiarities which 

 render them deserving of notice. 



The morning was very hot, and the sun very bright. Shortly 

 after mid-day the atmosphere began to become hazy, especially 

 towards the S. : a close and oppressive sensation was complained of. 

 Small whirlwinds carrying up dust were seen in different parts 

 of the plain on which the station is built, and not only was their 

 circular motion different in different individuals, but their onward 

 progress was in different and independent directions, while again 

 in other parts of the plain a column of dust would be observed 

 suddenly to rise from the ground, without any evident circular 

 motion, but with a slight curve at its lower extremity, the convexity 

 being directed forward, thus, 



) 



