Philosophy of Storms. 123 



ratures, it follows that a pound of steam being condensed into 

 1198 pounds of water at 32° would heat it up 1°. And as the 

 specific caloric of air is only 0.267, if a pound of vapor should 

 be condensed into 1198 pounds of air, it would heat that air 

 nearly 4°, or which is the same thing, it would heat 119 pounds 

 of air 4°, or 100 pounds 48°, and in all these cases it would ex- 

 pand the air about 8000 times the bulk of water generated ; that 

 is, 8000 cubic feet for every cubic foot of water formed out of 

 the condensed vapor. And as it requires between 1300 and 1400 

 cubic feet of vapor, at the ordinary temperature of the atmos- 

 phere, to make one cubic foot of water — if this quantity be sub- 

 tracted from 8000, it will leave upwards of 6600 cubic feet of 

 actual expansion of the air in the cloud for every cubic foot of 

 water generated there by condensed vapor. 



This great expansion of the air in the forming cloud will cause 

 the air to spread outwards in all directions above, causing the ba- 

 rometer to rise on the outside of the cloud above the mean, and 

 to fall below the mean under the middle of the cloud as much 

 as it is known to do in the midst of great storms. 



For example, if the dew point should be very high, say 78°, 

 then Ihe quantity of vapor in the air would be about one fiftieth 

 of its whole weight, and if the up-moving column should rise 

 high enough to condense one half its vapor into cloud, it would 

 heat the air containing it 45°, and the air so heated would be 

 ^Yoths larger than it would be if it was not so heated. And if 

 we assume a case within the bounds of nature, and suppose the 

 cloud and the column under the cloud to occupy three fourths of 

 the whole weight of the atmosphere, or in other words, if we 

 suppose the top of the cloud to reach a height where the barom- 

 eter would stand at 7J inches, and the mean temperature of the 

 whole column 40° warmer than the surrounding air, then would 

 the barometer fall under the cloud at the surface of the earth 

 ^Yflths of 22.5, or a little more than two inches. 



Though the air may be driven up by the ascending column 

 much higher than the point assumed in the last article, the cloud 

 will cease to form at greater heights, because the dew point at 

 these great elevations, falls by a further ascent as rapidly as the 

 temperature — and at greater elevations, it will even fall more 

 rapidly. If for instance the air should rise from where the ba- 

 rometer stands at six inches to where it stands at three inches, 



