The descriptions and conclusions herewith presented are based on observations made during the course of the geologic mapping of six 15-minute quadrangles in southern Indiana and Illinois for the U. S. Geological Survey. Most of the evidence was obtained from the Mount Carmel, Princeton, and New Harmony quadrangles, or those crossed by the Wabash river, though a number of minor, yet important features bearing on the loess problem were noted in the Haubstadt, Boonville, and Petersburg quadrangles to the eastward (figure 1). With the exception of the dunes of probable late Winconsin stage, occurring along the border of the Wabash valley, and the recent flood-plain deposits bordering all but the smallest streams, the entire surface of these quadrangles is covered with a mantle of fine silts. Up to the present time no attempts to differentiate these silts have been made, the whole mantle apparently being regarded as a unit . . .