INVESTIGATION OF STORMS. 181 



eight thousand cubic feet for every cubic foot of water thus 

 formed and congealed into snow. This great expansion 

 would cause the air to swell up to a greater height on the 

 east side of the central line of the storm than on the western 

 side. 



The air, then, in the upper part of the atmosphere would 

 roll off from the east towards the west, diminishing its 

 weight on the east of the central line, and increasing it on 

 the western side ; and its violence would be augmented, or 

 diminished, as it passed over the country with a higher or 

 lower dew point. Moreover, the particles of snow would 

 be carried up to a great height by the ascending air, on the 

 east side of the central line, and thus become excessively 

 cold, and in falling down through the air on the west 

 side, would diminish its temperature very much, and cause 

 the barometer to rise, on the west side, both by their own 

 weight, and by the increased weight af the air, by cold. 



142. This cold air covered the whole country from Mich- 

 igan to the eastern coast of the United States, till the begin- 

 ning of the great storm of the 26th January ; and, what is 

 worthy of particular notice is, that the temperature began 

 to increase first in the north and north west. On the morn- 

 ing of the 25th, in the north western parts of Pennsylvania 

 and northern parts of New York, the thermometer had 

 already risen in some places 30, and in others above 40. 

 While in the south east corner of Pennsylvania and in 

 the south east corner of New York, it had not begun to rise. 

 The wind also began to change from theaiorth west to south 

 and south east, first in the north west parts of Pennsylva- 

 nia and New York, some time before it commenced in the 

 south east of those states ; and during the whole of the 25th 

 the thermometer in the north of New York continued to 

 rise, though the wind was blowing from the southward, 

 where the thermometer was many degrees lower. What 

 was the cause of this sudden increase of temperature in a 



