Reviews—United States Geological Survey. 4.29 
or in the adjacent sedimentary formations at a corresponding horizon. 
Mr. G. F. Loughlin describes the recent alunite developments near 
Marysvale and Beaver, Utah. The feasibility of extracting potassium 
sulphate from alunite, which is the double sulphate of aluminium 
and potassium, was demonstrated by Mr. Waldemar T. Schaller, and 
there appears to be good hope of utilizing it as a commercial source of 
potash salts; also the alumina obtained as a by-product may prove of 
commercial value. All the deposits as yet found seem to be veins 
cutting porphyry (altered dacite); the veins are distinctly banded, 
nearly pure alunite alternating with quartz. 
Mr. Edson S. Bastin and Mr. James M. Hill report on the economic 
geology of Gilpin County, Colorado. The ores are divisible into five 
groups: (1) gold-silver ores, the main economic resource of the 
region; (2) uranium ores, interesting as a source of radium; 
(3) tungsten ores, forming the basis of the tungsten industry of Beaver 
County; (4) copper ores, poor in precious metals; (5) titaniferous 
iron ores, of no commercial value. The entire area is underlain 
by the pre-Cambrian rocks constituting the core of the Front Range. 
Probably in early Tertiary time igneous rocks of many varieties were 
intruded as dykes or stocks. Surface deposits formed by glaciers 
or streams are the only other formations present. 
Mr. W. T. Schaller writes upon cassiterite in San Diego County, 
California. The pegmatite dyke yielding the cassiterite crops out on the 
east side of Chihuahua Valley, about two miles south of the boundary 
between Riverside and San Diego Counties on the edge of the gem 
district. 
In the second part Mr. C. E. Lesher describes a compact and 
convenient field apparatus for determining ash in coal, which weighs, 
inclusive of the case, about thirty-four pounds, and measures about 
a foot cube. 
The Healdton oil-field, Carter County, Oklahoma, discussed by 
Mr. Carroll H. Wegemann and Mr. Kenneth C. Heald, was discovered 
in August, 1913. The oil has probably been derived from the 
Pennsylvanian rocks underlying the Permian Series. The accumu- 
lation of oil is undoubtedly due to the presence of rock folds. 
Mr. Wegemann also treats on similar lines of the Loco and Duncan 
gas-fields in Stephens or Jefferson Counties, Oklahoma. Mr. Eugene 
Stebinger investigated the geology and coal resources of Northern 
Teton County, Montana. The coal, which is of medium bituminous 
grade, occurs in the Two Medicine and the St. Mary River formations. 
The former with the underlying Virgelle sandstone is identical with 
the rocks called the Belly River series by Canadian geologists. 
Fossils are abundant, and include vertebrate, plant, and molluse 
remains of many species. The rocks of the St. Mary River formation 
consist mainly of clay and clay shale, and partly of consolidated 
sand. Bone fragments of undetermined Dinosaurs are abundant. 
Mr. Charles T. Lupton describes the oil and gas near Basin, Big 
Horn County, Wyoming, and Mr. D. Dale Condit the structure of 
the Berea oil sand in the Woodsfield and Summerfield Quadrangles, 
Ohio. In the latter instance, the rocks at the surface are included in 
the Conemaugh and Monongahela formations of the Pennsylvanian 
