Bartlett—The Cold-Waves of South-Central Wisconsin. 291 
a cold-wave prediction. This transfer would require, with the 
average wind velocity at Madison during January of 10 miles 
per hour (for all directions; northwest winds average greater 
velocity), and provided no heat was taken up by the air from 
the earth during its southeastward movement, a period of 40 
hours, nearly twice the time limit of the official cold-wave. It 
frequently happens that a temperature difference much greater 
than the average exists between Madison and the eastern 
boundary of the Dakotas, so that a northwest wind could pro¬ 
duce the necessary temperature fail within the required time. 
Text Fig. 1. Wind rose showing average temperature of winds 
from the different points of the compass during the winter months 
at Madison, Wis. The circle represents the average monthly tern* 
perature during the period considered. 
In considering the general winter temperature conditions it 
is also of interest to note the average warmth of winds from 
the different points of the compass. This is shown, for Madi¬ 
son, by the accompanying wind-rose, Text Fig. 1, from which it 
may he seen that northwest winds have an average tempera- 
