Add to ORKGWhile exploring Adair County in the interest of the Iowa State Geological Survey, the writer made some observations upon the surface soil of that region, which have led him to differ with the conclusions of other geologists who have described the same soil in adjoining counties. This soil has usually been described as Iowan loess, sometimes simply as loess. The long controversy as to the nature and origin of the Mississippi valley loess has left in its trail such apparent confusion as to the precise meaning of the term that it seems almost necessary to define it anew before attempting to make use of it in a scientific way. The writer will accordingly begin his argument by defining what he understands by the term “loess.