1850.] On the Bust-storms of India. 393 



and agitated ; soon the cloud is seen to approach and join the latter, 

 involving both extremities in one column having a spiral motion, and 

 on it moves or continues stationary. The power of electricity in raising 

 bodies, when combined with this peculiar whirling motion, will account 

 for fish, &c. being carried up in its vortex and afterwards discharged to 

 a distance on the earth. The motion of the dust-storm may be de- 

 scribed by spinning a tee-totum on a drop of ink ; and the way in which 

 bodies are projected may be in like manner described, by letting fall a 

 drop of ink on the centre of a tee-totum while spinning. In this case 

 the particles of ink are thrown off at tangents ever varying, as the 

 centre moves ; and perhaps it will be found, that when these kind of 

 storms pass through forests, trees uprooted are distributed something 

 in this manner. 



The violent dust-storms are by some supposed to commence at the 

 foot of the hills. I cannot tell if this be the case or not, but should 

 think that they do not necessarily do so, as many often originate in 

 extensive arid plains ; and the rarefaction of air, from great and long- 

 continued heat, may be in some way connected with the exciting 

 cause. 



Some of them come on with great rapidity, as if at the rate of from 

 40 to 80 miles an hour. They occur at all hours, oftentimes near 

 sunset. 



The sky is clear, and not a breath moving ; presently a low bank of 

 clouds is seen in the horizon, which you are surprised you did not ob- 

 serve before ; a few seconds have passed, and the cloud has half filled 

 the hemisphere : and now there is no time to lose — it is a dust-storm, 

 and helter-skelter every one rushes to get into the house in order to 

 escape being caught in it. 



The electric fluid continues to stream down the conducting wire 

 unremittingly during the continuance of the storm, the sparks often- 

 times upwards of an inch in length, and emitting a crackling sound ; 

 its intensity varying with the force of the storm, and, as before said, 

 more intense during the gusts. 



Many dust-storms occur at Lahore and in the Punjaub, generally 

 during the hot and dry months, as many as seven and nine in one 

 month. 



One that occurred last year in the month of August seemed to have 



