CHARACTER, ORIGIN, OCCURRENCE, AND USES. 33 
alumina ; in others they are a true kaolin, a hydrous silicate of alumina. 
In Arkansas, as in southern France and in Ireland, where similar 
deposits occur, they are associated more or less intimately with 
eruptive rocks. They occur in pockety deposits of uncertain dis- 
tribution, with a tendency to form horizontal lenticular beds varying 
greatly in thickness as well as in character. Their origin is involved 
in some obscurity/' 
a The most comprehensive report on Arkansas bauxite is that of Dr. C W. Hayes, published in 
Twenty-first Ann. Rept. U. S. Geol. Survey, 1899-1900, pt. 3, pp. 441-472. An earlier paper by J. C. 
Branner (Jour. Geology, vol. 5, 1897, pp. 263-289) contains a brief bibliography of bauxite. 
48136— Bull. 351—08 3 
