126 
HAROLD’S DISCUSSIONS. 
The map of November 1st shows that the wind 
throughout the Mississippi valley was northwest and 
north. This would indicate that there is a low ba¬ 
rometer somewhere in the Grulf. The conclusion 
proved correct, for the next day the “ low ” from the 
Gulf moved into Alabama. 
On November 1st the barometer was 30.2 in 
Manitoba and 29.9 at Chesapeake Bay, a difference 
of 0.3 inches in the pressure of the atmosphere. We 
would naturally expect the air to flow from the former 
to the latter region ; but instead, it flowed from Man¬ 
itoba toward Alabama, although the barometer on the 
Gulf coast was thirty inches, or one-tenth higher than 
at Chesapeake Bay. The deviation of the air currents 
from an easterly to a southerly direction, it seems to 
me, was caused by the Appalachian Mountains, the 
Mississippi valley becoming, as it were, a trough for 
the air to flow in. 
Let us now look at the direction of wdnds about 
a “low.” In Alabama, on the 2d of November, the 
wind blew toward the center of low pressure from 
the north, northwest, west, and northeast. This is 
fairly illustrative of the direction of the wind about 
a “ low ” (Fig. 63). 
After examining maps for a number of days, I 
was convinced that the atmosphere moves spirally 
around the center of low pressure, and in the direc¬ 
tion contrary to the movement of the hands of a watch 
if laid down face upward. These regions have there¬ 
fore received the name of cyclonic centers; “ highs ” 
are known as anticyclonic centers. 
