THE SOIL SURVEY 737 



632. The extent of soil surveys in the United States. ■— 

 The detailed survey and mapping of soils by the Bureau 

 of Soils of the United States Department of Agricul- 

 ture, according to the scheme outlined above, has been in 

 progress since 1899. On January 1, 1915, about 330,000 

 square miles had been covered by detailed surveys and 

 435,000 square miles had been covered by reconnoissance 

 surveys. In addition, several miscellaneous surveys have 

 been made in outlying provinces such as Porto Rico, 

 Panama, Philippine Islands, and Alaska. The total num- 

 ber of soil types and series recognized is approximately 

 2000 and 600 respectively. 



633. Surveys by state institutions. — Several states 

 are engaged in soil survey work, either independently or 

 in cooperation with the tJnited States Bureau of Soils. 

 The states that have undertaken this work independently 

 have carried it out in the same general manner as in the 

 Federal survey. Some of the states that are working 

 independently have confined their investigations to recon- 

 noissance surveys on a large scale. Tennessee has pub- 

 lished a general report, with a map, on the soil areas of 

 the state, with special reference to their geological rela- 

 tions. Accomt is also taken of the tenure, chemical 

 composition, and other properties. Iowa, Missouri, and 

 Illinois and Ohio ^ have published similar general reports 

 showing soil areas based chiefly on origin. Illinois, In- 

 diana, and New Jersey have also published detailed reports 

 on particular areas. In their work the principles of clas- 

 sification laid down above have been followed in a general 

 way, but with emphasis on certain selected properties. 



^ Coffey, C. N., and Rice, T. D. Reoonnoissanee Soil Surrey 

 of OUo, U. S. D, A., Bur. SoHs, Field Op., p. 134, 1912, 



