41 



prey to several factors no one of which exerted outstanding control. 

 For example, on May 13 a slight shallow depression moved from 

 Illinois eastward to the Potomac and the next day spread into a 

 spacious depression with two centers. One traveled eastward while 

 the other remained stationary until two days later it coalesced with 

 a third depression which had been drifting slowly eastward from the 

 Great Lakes. Contemporary with this modification in the weather 

 we noticed that the wind velocities in general had gradually become 

 less than they had been earlier in the season. 



Fig. 7. — June cyclone tracks 



May 25 to 30 an anticyclone of vast proportions expanded from 

 the region of central Canada and spread over the entire eastern half 

 of the United States and extended out to include the ice regions. It 

 finally divided into two centers and soon afterward disintegrated 

 completely. It is interesting to examine the flatness of the baro- 

 graph curve and the presence of clear weather, both of which are 

 recorded on Figure 3, page 35. 



JUNE 



The most important lesson contained in the cyclone tracks for 

 June (fig. 7) is obtained by comparing the position of the average 

 with the position of the average for the months of March and April. 

 It is clearly indicated that a migration to the northward of the mean 

 cyclone track took place in the course of two months. It is estimated 

 as approximately 150 miles. The explanation for track C, Figure 7, 



