REVIEWS 739 



gested. The characteristic pisolitic structure of the upper portion of 

 the deposits indicates chemical precipitation. The granitic bauxite 

 forming the lower or basal portions of the beds, and the bowlders, are 

 evidently of a different origin. The bauxite was probably laid down 

 on the syenite rather than on the kaolin, as there is no indication that 

 the kaolin is an intermediate product between the fresh syenite and 

 the bauxite. 



In his report on the igneous rocks of Arkansas Dr. J. Francis Wil- 

 liams suggests two theories for the accumulation of the bauxite. 

 First, that the bauxite was formed by the decomposition of a bed of 

 clastic material, derived principallv from the syenite. The second, 

 which he regarded as the most probable one, involved the action of 

 the waters of the Tertiary sea on the still highly heated igneous rocks, 

 in which, under high temperature and pressure, the constituents of the 

 syenite were dissolved and brought to the surface in solution, the 

 water emerging as hot springs. In the discussion of these theories 

 Dr. Hayes points out serious difficulties to both. 



In the last part of the report Dr. Hayes treats of the " Economic 

 Relations" under "Development;" "Amount of Ore," which includes 

 a tabular statement of the estimate of the amount of ore in the Arkansas 

 bauxite region, and, according to the author's calculations, shows the 

 total amount estimated in outcrops to be 6,608,500 long tons, and the 

 total amount under cover 43,711,200 long tons; "Quality of the 

 Ores ;" and " Mining and Preparation of the Ore for Market." 



Thomas L. Watson. 

 Denison University, 

 Granville, Ohio. 



