291 Professor Mitchell on the Proximate Causes 



I can account for all the phenomena, only by supposing 

 that a vortex or horizontal whirlwind, or rather a succession 

 of them, is established in Georgia, and passes gradually over 

 the United States. The existence of such a vortex creating 

 a wind from the north-east at the surface of the earth, is ob- 

 viously not incompatible with an actual transfer of the whole 

 body of the atmosphere, incumbent upon the United States from 

 the south-west. It is probable, however, that the transfer 

 is from the north-east. The warm air of the ocean saturated 

 with moisture is in this way brought over the land ; it is lifted 

 by the vertiginous motion that has been created, and pro- 

 pagated along the coast into the upper regions of the at- 

 mosphere, and the Intensely cold air of these regions brought 

 down to the surface. It is believed that in this way, and in 

 no other, we can account for the phenomena of our north-east 

 storms. A (c) D B 



During a nine days' passage from New York to the Capes of 

 Virginia, in the summer of 1829, I had ample opportunity of 

 observing the movements of the air during the prevalence of 

 those light baffling breezes by which the ocean is occasionally 

 swept in calm weather. The water is seen roughened by the 

 wind in the direction from which it is afterwards found to blow, 

 as at C, every other part of the ocean probably, except the 

 tract immediately about C, being perfectly smooth. It is calm 

 at A beyond the place of the breeze, at B the place of the ves- 

 sel, and in the intermediate space at D. The roughness gra- 

 dually approaches the vessel, reaches it, fills the sails for a mo- 

 ment, and papses by. How are these appearances to be ac- 

 counted for ? It is not a vacuum at B that urges the breeze 

 forward, for that would set the air overhanging the whole in- 

 termediate space, that at D for instance, in motion, before there 

 would be any movement at C. The effect is not produced by 

 a portion of condensed air seeking to expand itself, as that 

 would swell and escape equally in all directions. But upon the 

 supposition of a vortex rolling over the surface of the ocean, 

 the explanation is simple and easy. 



The following statement, quoted by Daniell from the " Ac- 

 count of the Arctic Regions," of a fact apparently of common oc- 

 currence in those latitudes, places in a clear and strong light the 



