Research Technique 140 
portant than the acreage of an ownership farm. Consequently, the 
acreage under the control of each farmer also was tabulated. 
At the outset of the study, an accurate base map was indispensable. 
Advance copies of topographic maps covering the American Bottoms 
were provided through the courtesy of members of the Illinois State 
Geological Survey. Photostats, with a scale of one inch to the mile, 
were made of the appropriate parts of these maps, and the photostats 
vere combined to form one map. A base map was derived from this 
topographic map. 
The location and acreage of each ownership farm was ascertained 
bya scrutiny of the assessors’ books and cross-checked in the field by 
Means of inquiries among farmers. Chief dependence for the delimita- 
tions of non-agricultural land — developed urban areas, developed 
suburban areas, and swamps not associated with operated farms — was 
Placed on field work, cross-checked by data on topographic maps and 
Plats of urban and suburban areas. Since an ownership farm was taken 
as the basic unit in collecting data, parts of the bluff slopes and u Jand 
Were included if they were portions of farms which also included parts 
of the flood plain. 
The boundaries of the ownership farms were placed on a base map 
Each farm was classified as to the type of agricultural economy repre- 
sented on the basis of the composition of the field crop pattern. This 
map provided the data for the construction of a map showing the dis- 
tribution of the sections with different types of agricultural economy. 
me RS Smith, Chief of the Soil Survey, College of Agriculture, 
the University of Illinois, provided advance sheets of a soil survey of 
St. Clair County and loaned the office copy of a soil map of Madison 
County. Mr. E. A. Norton, associated with the Soil Survey, supplied 
a table correlating the soil types of the two counties. The soil types 
Were checked against the practical classification of farmers. The chief 
Outcome of this cross-checking was the construction of a simplified soil 
— including five major types of soil, considered from the esa 
of recognized differences by practical farmers. The distribution of soi 
types has been shown on a map which includes the boundaries of the 
4gricultural sections, in order to facilitate a comparative study of the 
relations of soil types to the types of agricultural economy. 
Drainage and levee districts——Private blue prints, showing farm 
boundaries and acreages, have been made of the several drainage and 
