370 Report on the Dust Whirlwinds. [No. 4. 



About 3 p. m. the whole sky became obscured and presented a 

 very peculiar appearance : several perpendicular columns of dust 

 such as that represented above, and varying greatly in diameter, al- 

 though all of nearly equal height were seen approaching from S. E. 

 their upper extremities blending as it were in a dark cloud appa- 

 rently containing much aqueous vapor as well as suspended dust. 

 At the same time, a mass of dust was seen advancing from N. E. 

 and several smaller columns such as have been noted, were being 

 driven onwards in various directions in our vicinity. 



These various columns seemed to break up, and instead of a 

 cyclone coming on, a moderate breeze set in, carrying with it masses 

 of dust. Occasional peals of thunder were heard in various direc- 

 tions, a few drops of rain fell, and about 8 or 9 p. m. the atmosphere 

 cleared up. 



It is to be regretted that no proper instruments were available to 

 observe the peculiar conditions upon which the phenomena just 

 described, depended. 



It appears that the two days succeeding that on which the above 

 modification of a storm took place were rainy, the wind cold, the 

 Ther. 70° F. in the shade. 



One or two points of great meteorological interest may be gather- 

 ed from the above remarks, viz. 



a. Numerous whirlwinds may, under certain circumstances take 

 place simultaneously within a very inconsiderable space ; yet with 

 independent motions, both as regards the circular current of wind 

 and onward progress. 



b. Currents of wind may be noted at their first commencement 

 in certain cases, by the column of dust they suddenly raise on a 

 dusty plain. 



c. These phenomena are attributed to electro-magnetic, or other 

 influences which the want of philosophical instruments renders us 

 unable to detect. 



13. — 12th April, 1853. Although there were numerous cumuli 

 and strati during the forenoon, the day was nevertheless clear, and 

 the sun at times shone very bright. About 1, 30 p. m. the wind at 

 the time being N. E. a magnificent mass of defined cloud appeared 

 JS.. "W". and soon assumed a distinctly arched form. Films of cloud 



