94f UNITED STATES* 



iina. And if at other times it bring snow itself in- 

 stead of rain, it is because in its aerial course it 

 meets with clouds from the north-east or east, 

 which had not time to turn back. But such snows 

 melt immediately, or are changed into rain as they 

 fall. Six hours continuance are sufficient to give 

 the south wind that character of heat and moisture, 

 which it derives from the tropical seas, whence it 

 originates. In summer, when it has more velocity 

 than usual, it presently brings on a storm : and it 

 has been remarked at Louisville, as well as other 

 places situate on the Ohio, that, if it continue for 

 twelve hours together, thunder will infallibly ensue* 

 Now reckoning its progress at a mean term of forty- 

 five or fifty miles an hour, a calculation v/hich the 

 experiments made on the velocity of winds render 

 plausible, this is just the time requisite to bring 

 clouds from the centre of the gulf of Mexico, 10 or 

 12 deg. distant. The frequency of the south wind 

 at this season proves, that a focus of suction then 

 exists in the north of the continent: but it remains 

 to be known, whether this focus lies beyond or on 

 this side of the Algonquin chain,* which skirts the 

 lakes on the north. This cannot be decided but by 

 corresponding observations on a line extending from 

 the shore of Florida, through Kentucky, Lakes ikrie 

 and Huron, and the Algonquin mountains, to the bor- 

 ders of Hudson's bay : and these would throw great 



* This chain of mountains, though represented as of iinmensfc 

 length and height by Mr. Volney in the map accompanying his work> 

 and placed between Canada and Hudson's bay has not yet been de* 

 scribed, Mr. V. ought to have given his authority for inserting 

 them. 



