Reviezv of Recent Geological Literature. 319 
The mountains of the Choctaw region are all of the same type and 
have similar detail of surface features. They are all of synclinal 
structure, and the same formations occur in all four of the mountains 
in this field and in nearly the same relative position. The sides of the 
mountains, knobs, peaks, or ridges have the bench and terrace type of 
sculpture. 
The geological structure, stratigraphy and economic features are 
clearly described. Regarding the distribution of the coal seams of the 
■district it is stated that "Seven workable beds of coal are known in the 
eastern Choctaw coal field. They occur in four different formations, 
from the top of the Hartshorne sandstone, which is the lowest coal- 
bearing rock known in Indian Territory, upward to the lower part of 
the Boggy shale. The thickness of the rock between the lowest and 
highest of these coals is estimated to be nearly 3,600 feet. Besides these 
■coal beds, which are profitably worked, there are a number of others 
that are thin and have been located, chiefly by prospect drill, in various 
parts of the McAlester shale and Savanna sandstone. 
"A knowledge of the geological structure of the rocks in which coal 
beds occur and of the combined effects of structure and erosion on 
the topography or surface configuration of the land is necessary to the 
most successful economic prospecting and exploitation of the coal. 
Except to test the thickness and quality of a particular coal bed, the 
drill need not be called into use in a coal field of this nature. All the 
l<nown coal beds are associated with sandstone beds of considerable 
persistency, which make their presence and location known by more or 
less elevated hills and ridges. When the interval between such sand- 
stone and coal beds is once established, the crop of the coal may be 
located as rapidly as the sandstone ridge or outcrop can be traversed. 
The dip of the sandstone may be determined at almost any point by 
measurements on its outcropping edges. The coal beds, on the con- 
trary, usur.ily lying in shale, have their edges worn down and concealed 
by soil and rock debris." 
Good maps accompany the memoir. Also a few paragraphs on the 
composition and adaptability of the coals. c. R. k. 
Geology and zvater resources of Nez Perce county, Idaho. I. C. 
Russell. (U. S. Geol. Sur., Water supply papers, Nos. 53 and 
54. leoi). 
This document is more than a treatise on the water supply and 
irrigation of Nez Perce county, for it enters largely into the inter- 
esting geology of the region, and presents some very fine plates show- 
ing the canons eroded by the streams. 
Prof. Russell notes two sharply defined rock groups — a pre- 
Tertiary and a Tertiary. The former embraces a large variety 
of rocks of both igneoois and sedimentary origin, and large areas 
of metamorphic rocks. These are disturbed by folding and other- 
wise and once formed a land surface that was deeply denuded be- 
fore the younger group was spread upon it. The Tertiary group 
consists largely of igneous rock, either basalt or volcanic tuffs, but 
