£. Loomis— United States Weather Maps. 13 
Classification of Storms. 
The storms which pass over the United States seem to be 
naturally divided into two distinct classes; the first class in- 
cluding those storms which come from the far west and nort 
west, the center of whose paths is generally north of lat. 40°; 
and the second class including those storms which come from 
the south and south west, and Mae sshaeiklly appear to origi- 
nate in Texas or the Gu If of Mexico. Storms of the second 
class are comparatively ‘afrequiiat forming only about one- 
sixth of the whole number of poege lin are almost un- 
known in the summer months, and are most frequent in the 
winter and spring. The majority of i tees have their origin 
west of the mouth of the Mississippi River, and their average 
course is N. 60° E., being 22° more northerly than the general 
average of storms, which would show the average direction of 
storms of the first class to be nearl y dueeast. Theaverage velocity 
of these storms does not differ much from that of storms of the 
first class. The majority of storms of the second class reach the 
Atlantic Coast before arriving at lat. 40° ; and from thence their 
ogee generally appear to be nearly parallel to the coast. One 
of these storms (Sct. 25, 1872) was diverted inland, and ad- 
vanced northward nearly to Rochester, after which it turned 
eastward in the direction of nerags Another storm Sr 
over Punta Rassa, in Florida, Ont 6, 187, 3, where the barometer 
in 14 hours fell ga 29°96 to 28 “40, and afterward the storm 
continued its course with diminished ‘severity, traveling north- 
eastward nearly parallel to the Atlantic Coas 
— approach of storms of the first class is usually indicated 
n the’ weather maps by the word /ow, at some point west 
0 ' the — i River north of lat. 40° generally i in Minnesota 
He uently we find the word low on the maps of 
0 or oe successive days, occupying nearly the same posi- 
tion, indicating either that the center of a storm was nearly 
stationary for 24 hours, or that the precise position of the 
. 8 center was undetermined, and it ek only be located at 
me distance westward. When the storm has adva vanced so fai 
iced that the exact position of its center can be assign 
it generally manifests a ue reference for the region of the 
northern lakes, particularly Lakes Superior and Huron ; and 
