United States Weather Maps. 11 
another and entirely distinct storm prevailed in the Gulf of 
Mexico; on the 6th it passed over Georgia; on the 7th it 
passed over Virginia, ae on the 8th it passed north of Lake 
ntario. This storm was followed by an unusual reduction of 
temperature in the southern States. Its effects were to some 
a 
each of the stations in column first; columns show the ob- 
servations of the thermometer at 75 35™ a. M.; and columns 9-14 
on either of the preceding days at Knoxville, Nashville, Cincin- 
nati, Louisville and Memphis. This fact, together with the 
form of the isabnormal curves (convex toward the north), indi- 
cates that the cold did not come from the north or northwest, 
but must have descended from the upper regions of the atmos- 
phere over the southern States. 
here are other considerations of a more general nature 
a 
general principle which I have been trying to establish. The 
P €nomenon in question is not peculiar to the United States 
ut prevails fur to the north of us, even to the coldest regions 
Which have ever been visited by man. It was found at Mel- 
ville Island, lat. 75° N.; it was found at Van Rersselaer Harbor, 
at. 781° N.; it is found in the coldest parts of Siberia. At 
Melville Island, on the 26th of December, 1819, during a strong 
wind, the barometer fell to 29°10 inches; it soon began to rise, 
and in four days it rose to 80°75, the highest point attained 
during the year. During the same time the thermometer fell 
from —5° to — 43°; the lowest temperature observed during the 
year. At Van Reusselaer Harbor, on the 28th of December, 
1853, during a severe gale, the barometer fell to 29°05, and in 
two days it rose to 3050. The thermometer during the same 
