THE ATLANTIC STATES. 209 



there must be a prodigious condensation of aqueous 

 vapour. If it be demanded, wherefore does this 

 change produce north-eastern gales only, why have 

 we not northern gales accompanied by the same phe- 

 nomena? the answer is obvious. The course of our 

 mountains is from the north-east to the south-west. 

 Thus no channel is afforded for the air proceeding 

 to the Gulf in any other course than that north- 

 eastern route which it actually pursues. The com- 

 petency of the high lands of Mexico to prevent the 

 escape over them of the moist warm air displaced 

 from the surface of the Gulf, must be evident, from 

 the peculiar dryness of their climate ; and the evi- 

 dence of Humboldt. According to this celebrated 

 traveller, the clouds formed over the Gulf, never 

 rise to a greater height than four thousand nine hun- 

 dred feet, while the table land for many hundred 

 leagues lies between the elevation of seven and nine 

 thousand feet. Consistently with the chemical laws, 

 which have been experimentally ascertained to ope- 

 rate throughout nature, air which has been in contact 

 with water, can neither be cooled nor rarefied with- 

 out being rendered cloudy by the precipitation of 

 aqueous particles. It follows then, that the air dis- 

 placed suddenly from the surface of the Gulf of 

 Mexico, by the influx of cold air from the north- 

 east, never rises higher than the elevation mention- 

 ed by Humboldt as infested by clouds. Of course, 

 it never crosses the table land which at the lowest is 

 2000 feet higher. 



Our north-western winds are produced, no doubt, 

 26 



