1850.] On the Dust-storms of India. 391 



Or nearly so ; and during the whole of this time the dust and mi- 

 nute bodies on the ground are kept whirling above into the air. In 

 other cases these small dust-storms are seen slowly advancing, and 

 when numerous, usually proceed in the same direction. Birds, kites 

 and vultures, are often seen soaring high up, just above these spots, 

 apparently following the direction of the column, as if enjoying it.* My 

 idea is, that the phsenomena connected with dust-storms are identical 

 with those present in waterspouts and white squalls at sea, and re- 

 volving storms and tornadoes of all kinds ; and that they originate from 

 the same cause, viz. moving columns of electricity. 



In 1847, at Lahore, being desirous of ascertaining the nature of 

 dust-storms, I projected into the air an insulated copper wire on a 

 bamboo on the top of my house, and brought the wire into my room, 

 and connected it with a gold-leaf electrometer and a detached wire 

 communicating with the earth. A day or two after, during the 

 passage of a small dust-storm, I had the pleasure of observing the 

 electric fluid passing in vivid sparks from one wire to another, and of 

 course strongly aifecting the electrometer. The thing was now explained ; 

 and since then I have by the same means observed at least sixty dust- 

 storms of various sizes, all presenting the same phsenomena in kind. 



I have commonly observed that, towards the close of a storm of this 

 kind, a fall of rain suddenly takes place, and instantly the stream 

 of electricity ceases, or is much diminished ; and when it continues, 

 it seems only on occasions, when the storm is severe and continues 

 for some time after. The barometer steadily rises throughout. In 

 this part of the world, the fluctuation of the barometric column is 

 very slight, seldom more than two or three tenths of an inch at a time. 



The average height at Lahore is 1-180, corrected for temperature, 

 indicating, I suppose, above 1150 feet above the level of the sea, 

 taking 30 inches as the standard. 



A large dust-storm is usually preceded by certain peculiarities in the 

 dew-point, and the manner in which the particles of dew are deposited 

 on the bulb of a thermometer. My mode of taking the dew-point is, to 

 plunge a common thermometer in a little ice, let it run down 20° or 



* They may be looking for prey, or involved in, and unable to fly out of, the in- 

 visible part of the electrified aerial column, of which the lower part only is visible 

 to us by the dust raised. — Ed. Journal. 



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