BULLETIN 1224, U. & DEPARTMENT OF AGRICULTURE. 
the basis for making further analytical studies of the data. In 
forming these groups effort was made to secure a rough uniformity 
in the economic and the general physical conditions in each district. 
No attempt was made to divide the entire country into homogeneous 
districts, but only to group the counties in this study so that they 
C O 
= 3 
53 o 
3-S 
IS 
would present a rough uniformity. Sufficient data were not avail- 
able to do this with complete accuracy. 
The heavy lines on the map (fig. 1) on page 4 show the groups. 
They are numbered from east to west in the northern part of the 
country and from west to east in the southern part. 
