Bartlett—The Cold-Waves of SouthWentral Wisconsin. 293 
conditions are sufficient to cause strong northwest winds. The 
cold air of the Dakotas is thus drawn rapidly southeastward 
over Wisconsin where a cold-wave results. Let us consider an 
actual case of this kind. 
At 7 a. m. on January 19, 1907, a storm of considerable 
strength was central in southern Minnesota (see Plate XVI). 
It had been attended at Madison, during the preceding 
night, by southerly winds and warm, cloudy weather, with 
rain, the temperature rising above 40°. During the 19 th this 
storm moved eastward to Lake Michigan, and by 7 p. m. at 
Madison the wind had shifted to northwest and the tempera¬ 
ture had fallen decidedly. Simultaneously with the easterly 
storm movement the High in Alberta developed in intensity 
and also moved eastward. Plate XVII shows the march of 
the meteorological elements at Madison during the passage of 
the storm and the approach of the anti-cyclone, and also shows 
the movement of the cold-wave across southern Wisconsin as 
indicated by the thermograph traces at several Weather Bu¬ 
reau stations. Prom the Madison data it is to be noted that 
the wind during the cold wave was from the west or northwest, 
with an hourly movement of 20 miles or more (a maximum 5 
minute velocity of 38 miles per hour was recorded) and that 
the barometric pressure was increasing rapidly. The simi¬ 
larity of the temperature falls at the various points is also note¬ 
worthy. This cold-wave was one of the most marked on record 
at Madison, the temperature falling 48° in 17 hours, from 
47° at 4 p. m. of the 19th to —1° at 9 a. m. of the 20th. 
The passage of another cold-wave which was of considerable 
interest on account of the damaging sleet storm which it 
attended is illustrated in Plate XVIII. This storm passed from 
Illinois northeastward across Wisconsin on December 27, 1904, 
and was remarkable for its low central pressure and the large 
amount of rain, sleet and snow which it caused. Its destruc¬ 
tive effects were chiefly due to breaking down trees and wires 
which had become overloaded with ice. The cold-wave ac¬ 
companying the storm as may be seen from the diagram, con¬ 
sisted in a fairly steady, rapid temperature fall, rather than a 
