[ 215 3 
fame latitude, may in a few hours wholly change 
the air of a particular diftrid : or, if from any pe- 
culiar circiimftance the air flicjlild become unufually 
dry, and confequently difpofed to difiblve much 
water, a great degree of cold might be almoO: in- 
flan taneoufly produced j but which could not be 
communicated to other bodies, in a little time, by 
lb rare a fluid as the air. 
During the forementioned degree of cold, a thick 
vapour was feen riling from the furface, and marking 
as it were the courfe of the river. If we attribute 
the elevation of this vapour to the attradion of the 
air, rather than to the comparative warmth of the 
water (for water juft beginning to freeze is oh- 
ferved not to lofe of its weight by evaporation i/2 va- 
cuo J the great cold may be thought perhaps, to have 
proceeded from the folution of water in air which 
was then carrying on ; for the earth was glutted with 
humidity, and the air was become dry, having been 
freed from its water by an almofl; inceflant precipi- 
tation for three davs, under the form of fnow or 
•f ' 
fleet. It is very remarkable, that the extreme cold, 
of January 13, 1709, came on at Paris, with- a 
gentle fouth wind, and was diminiflied when the 
wind changed to the north j this is accounted for by' 
M. de la Hire, from the wind’s having pafled over the 
mountains of Auvergne to the fouth of Paris,, then; 
covered with fnow j and by Mr. Homberg, froini 
the reflux of that air, which had been flowing, for 
fome time from the north. I do. not fee from w^hat 
philofophical principle it can be fuppofed, that the 
lame air in its regrcfs from a fouthern latitude fliould, 
b®L 
