188 Transactions of the Academy of Science of St. Louis 
belt two to eight miles in width. The flatness of the surface is 
clearly shown in Figure 8 
The Cuivre River has intrenched itself in this terrace form- 
ing a cut through it, 40 feet or more in depth and nearly a quarter 
of a mile in length, just south of Chain-of-Rocks, Lincoln County, 
Missouri. (Fig. 9). The village is in Lincoln County; but since 
the Cuivre River is here a boundary line, the cut is really in 
Cuivre township, St. Charles County. This Chain-of-Rocks 
should not be confused with the better known locality of the 
same name on the Mississippi River at the northern end of St 
Louis. For the locality on the Cuivre River the expression Chain- 
of-Rocks, Lincoln County, wiil be used; for the other locality, 
Chain-of-Rocks, St. Louis. 
A vertical section was measured a short distance south of 
Chain-of-Rocks, Lincoln County, and is shown in Table II. The 
terrace is composed of layers of rather fine sand, silt and clay. 
These strata are on the average approximately three feet in 
thickness and none is less than one foot. Wherever the terrace 
has been examined, relatively thick layers similar to these have 
been observed. Due to the excellence of the exposure in Cuivre 
township, St. Charles County, the name Cuivre Terrace is as- 
signed to the terrace. 
In addition to the extensive distribution of the Cuivre Ter- 
race along the great bend of the Mississippi above Grafton, the 
terrace can be traced in many other localities. Within the limits 
of the Middle Mississippi River Region it is exposed over great 
areas along Wood River, Illinois, and in the flat extending 
southward to the vicinity of Cahokia Creek, north of Edwards- 
ville, Madison County, Illinois. In this part of the terrace the 
stratified nature of the alluvium, for about 40 feet below the 
surface, is clearly shown in various cuts. In some places the allt- 
vium is covered by more or less loess. Two erratics were dis- 
covered in the alluvial material. A well-rounded cobble of pink 
granite, weighing about ten pounds, was picked out of the side of 
