Attempt to explain the formation, or development, of 

 the cumulus or thunder cloud on the principles laid down 

 by Mr. Espy in his Philosophy of Storms, modified some- 

 what as to the principle of the ascent of the air in the tor- 

 nado and water spout. 



On the 9th of August, 1852, a large cumulus cloud was 

 observed in process of development, the cloud was soon 

 capped by a dense, white vapor, (as if by a veil), showing 

 that the air above the cloud was being lifted bodily (as it 

 were) by the ascending column of hot air, above the dew 

 point. 



The dry bulb thermometer stood at 79° F., wet bulb 

 at 69° F., the dew point being at 65° F. 



The rain was soon seen to fall and in a few moments 

 the lightning was observed, followed, at an interval of 45 

 seconds, by a clap of thunder. A heavy shower from this 

 cloud fell at Hampton Falls. 



Reckoning a fall in temperature of 1° for every 100 

 yards, the base of the cloud was about 1,400 yards above 

 the surface of the Earth, and the top of the cloud about 

 three times as high, or 4,200 yards. 



If we suppose with Mr. Espy that the air cools in ascen- 

 ding at the rate of 1.5° for every hundred yards, the ther- 

 mometer in and outside of the cloud would indicate a fall 

 of 60° in the temperature in ascending 4,000 yards, unless 

 warmed up by the condensation of the vapors in the cloud. 



By the above ratio of descent of temperature, when the 

 air has risen 1,700 yards, the temperature will have fallen 

 between 25 and 26°, and in so doing, will, (according to 

 Dalton's tables) after making due allowance for the in- 

 creased space it occupies in ascending three miles, viz.: 

 one-third, condense forty-four one hundred and fifteenths 

 nearly of its vapor; which would be sufficient to heat up 

 the air in the cloud 35°. 



The expansion of the air in the cloud by the giving out 

 of this amount of latent heat, viz.: 35,° would equal thirty- 

 five four hundred and eightieths or one-fourteenth nearly, 

 of its bulk, or of the space occupied by the ascending 

 column of hot air. 



Supposing now the base of the cloud to be at one mile 

 above the earth, where the barometer rnav ' ie taken as 



