E. Loomis— United States Weather Maps. 3 
April, 1873, the path of a storm center 
near Chicago was such as is shown b 
the lower curve. In the latter case the 
direction of progress changed 860° in 
a little more that 24 hours, and in both 
cases the actual motion of the center 
was for several hours westward, at the 
rate of from 10 to 15 miles per hour. 
If then we take into account the actual 
motion of a storm’s center from hour to 
hour, we find that the storm path may 
have every possible direction, and the velocity of progress may 
vary from 15 miles per hour toward the west, to 60 miles per 
It thus appears that the inequality in the direction and 
velocity of storm paths is so great that a knowledge of their 
mean values affords but a very uncertain guide in predicting 
the progress of a storm from day to day. I have, therefore, 
sought to determine what are the most important disturbing 
causes which affect the velocity and direction of storm paths. 
For this pu I have tabulated nearly all the materials 
afforded by the weather maps, and compared them with the 
velocity and direction of the storm pa 
Influence of rain-fall upon the course of storms. 
near the Atlantic coast of the United States. The smallest oval 
