286 PHILOSOPHY OF STORMS. 



The barometer stood uncommonly high just before and just 

 after this storm. On the 19th, at 2, P. M., the barometer 

 at Philadelphia is marked, in my journal, maximum 30.73, 

 and on the 22d, at 7, A. M., it had risen again to 30.61 

 the minimum is not marked, but on 21st, at 7, A. M., it 

 stood at 29.65. These maxima were produced by the out- 

 spreading of the air in the upper regions from the centre of 

 the storm. The formation of cloud enough to make one 

 inch of rain, would give out latent caloric sufficient to ex- 

 pand the air in the region where the cloud was formed, 

 about one forty-eighth of its whole bulk, and cause the at- 

 mospheric column to be at least a mile higher in the centre 

 of the storm than at some distance from its borders, provi- 

 ded the expansion took place only upwards : but this it 

 could not do. Part of it would plainly spread outwards, 

 and thus cause the barometer to rise on the outside of the 

 cloud, at the same moment that it fell under the middle of 

 it. A most conclusive proof that this was the case will be 

 found in this : the barometer rose on the morning of the 

 19th, 0.08 of an inch at Philadelphia, from 30.65 to 30.73, 

 and yet the wind at that time, in most of the eastern States, 

 was westwardly, and at most of the western forts it was east- 

 erly ; at Philadelphia it was nearly calm. Now these cur- 

 rents below, blowing both ways from Philadelphia, certainly 

 tended to make the barometer fall there. The conclusion 

 is, that the supply of air was from above. 



As to the possibility of a storm passing the Rocky Moun- 

 tains, perhaps Professor Loomis is correct in deciding that 

 it could not. And yet a storm on the western side might 

 probably be the means of generating one on the east side in 

 the following manner. The latent caloric evolved by the 

 condensing vapor of the storm on the west side, would 

 cause a flood of air to swell up and roll over the mountain 

 to the east. The first effect of this would be to raise the 

 barometer on the east side. This would produce a western 



