CXXXIV 



standing at 30 inches and the density of the air at unit} - , 

 or one ; at four thousand two hundred yards, its density 

 would be .630, or one third less : or in other words the 

 barometer would stand at 20 inches at or' just above the 

 cloud, and at 30 inches at its base : one-fourteenth of this 

 difference would equal .71 of an inch of barometric pressure, 

 which would express the fall of the barometer from expan- 

 sion by the heat given out by the condensation of the 

 vapors if the expansion was all in an upward direction. 



On the supposition that the column of heated air or the 

 cloud ascends to a point where the barometer would stand 

 at 20 inches, the amount of rain which would fall would 

 be about 1.6 inch, supposing all the vapors to be condens- 

 ed and to fall on an area equal to the base of the cloud ; 

 and it would occupy about 30 minutes in falling : for when 

 the dew point is at 65° the air contains about one seventy- 

 seventh of its weight of vapor, and air at 80° dew point 

 ascending on the principle of floating bodies, at the rate of 

 7 1-2 feet in one second, at 65°, would rise one tenth less 

 rapidly, or at about the rate of 6 feet and 9 inches in a 

 second. 



Without doubt the Sun may and does, in the daytime, aid 

 in the development of the cumulus cloud. We learn from 

 Mr. Wise, the Aeronaut, that the air in the base of and on 

 the sunny side of the cloud is much warmer than at other 

 parts, and these clouds are seldom formed in the night ; but 

 we apprehend that the electricity given off by the conden- 

 sation of the vapors is, in many of these clouds, especially 

 those giving rise to the tempest or tornado and the water 

 spout, the great expansive power in their development: in- 

 deed, on no other principles but that of the convective dis- 

 charge of electricity can be explained the uplifting and re- 

 moval to great distances of heavy bodies, the drying up of 

 ponds, or the phenomena noticed in the subjoined account 

 of the tornado which has so recently occurred in Wisconsin. 



"An awfol tornado nearly destroyed the village of Yiroqua. Wiscon- 

 sin. Thursday week. One hundred -and seventeen persons were killed 

 and wounded. A correspondent of the N. Y. World gives the follow- 

 ing particulars : — 



The southern part of the village, for a strip near eighty rods in width, 

 was swept away. Where stood handsome white houses, neat barns, and 

 out buildings, nothing now remains but ruins. Gardens, garden fenc- 



