182 PHILOSOPHY OF STORMS. 



region bordered on the south with cold air, on the morning 

 of the 25th, when the thermometer had already risen at St. 

 Lawrence, in the north, from 17 to + 27 ; while it yet 

 stood in the south east part of New York, at Clinton Acad- 

 emy, + 10, and at Mount Pleasant + S? Was it the 

 evolution of latent caloric in the incipient storm, then ap- 

 proaching from the north west? It might be objected to 

 this suggestion, that the latent coloric is given out in the 

 region of the clouds, and not in the lower air at the surface 

 of the earth, and that, as air is a bad conductor, it could 

 not convey the caloric down so as to affect the temperature. 

 To this I answer, that though air is a bad conductor, or 

 even a non-conductor, yet it must have the power of radia- 

 ting caloric, or it would never get rid of the latent heat 

 which it always receives in the formation of clouds. No- 

 thing is more common than for the temperature to rise rap- 

 idly on the approach of a great snow storm. 



143. It seems highly probable that this rise is partly due 

 to the increased temperature and increased radiation of the 

 upper air, which has then spread out over our heads from 

 the approaching storm. Further observations are much to 

 be desired on this -point. 



144. If the storm commenced in the neighborhood of the 

 great lakes, and did not come from a great distance through 

 Upper Canada, no doubt the upmoving column of air origi- 

 nated there from the greater heat and higher dew point of 

 the air in contact with the waters of those lakes, which at 

 that time would be30 or 40 warmer than the air all round 

 those lakes. This circumstance would only account for the 

 commencement, but not for the continuance of the storm, 

 nor for the increase of temperature round its southern bor- 

 ders. 



