SURVEYS BY THE UNITED STATES BUREAU 115 



(1902), showing all of the upland, comprising 85 per cent of the 

 county, as one soil type (Marion silt loam), with the detail soil 

 map published by the University of Illinois Agricultural Experi- 

 ment Station (1911), showing eleven different types of upland 

 soil, most of which are commonly recognized by the local farmers, 

 the most extensive type (gray silt loam on tight clay, or " typical " 

 Marion silt loam) comprising only 37 per cent of the county. 

 These upland soil types vary in agricultural value from $15 to 

 $60 an acre. They vary in average composition from uoo pounds 

 of nitrogen and 40x3 pounds of phosphorus to 3890 pounds of nitro- 

 gen and 820 pounds of phosphorus in 2 million pounds of the sur- 

 face soil. On more than 15,000 acres of the level upland prairie 

 soil, surface drainage can be provided only with much diffi- 

 culty, while 40,000 acres of .eroded timberlands are so rough 

 that the soil ought not to be kept under cultivation. About 30 

 per cent of the upland is not underlain with tight clay, while the 

 remainder has the subsoil sometimes called " hardpan " by the 

 resident farmers. 



These facts are mentioned in order that the student may under- 

 stand that the soil survey as made by the Bureau of Soils is not 

 intended to be in sufficient detail for local, specific use. To quote 

 Professor Whitney's language from a letter to the author under 

 date of March 26, 1903: 



"In the work on the scale in which the Bureau is engaged, we cannot recog- 

 nize differences that might and should be recognized in a more detailed survey 

 of a limited area. It is necessary for us to show only important differences in 

 the soils which will be of value to the people of large areas. " 



Nevertheless, the soil surveys of the Bureau have large value as 

 a source of general information concerning the soils of the United 

 States. The author has very great respect for the art of surveying 

 soils, whether for general information over broad areas or for spe- 

 cific use where the details are mapped. 



The accompanying map of the United States, showing " Soil 

 Provinces," as published by the Bureau of Soils, is based in part 

 upon the work of the United States Geological Survey. Within 

 these 14 great soil provinces, the Bureau of Soils had recognized 

 (previous to January i, 1908) different soil types to the number of 



