776 
there have been three periods of eruption since 
the Middle Tertiary: (1) That of basic ande- 
sites, terminating in outpourings of rhyolite. 
(2) That of spongy porous rocks and ashes, 
marking the beginning of a tranquil period. 
(8) That of the basalts, continuous with Quater- 
nary volcanic eruptions in various parts of the 
Sierra. The second period was marked by cir- 
culation of thermal waters in the fissures lead- 
ing to the deposition of quartz with the sul- 
phides. 
The intimate structure of the veins, their vari- 
ations in relation to the adjacent rocks and to 
each other, as well as the distribution of ores, are 
considered in a chapter by the same authors. 
Sanchez contributes a mathematical discussion 
of the fracture systems, arriving at practically 
the same conclusions with Daubree. Ordofiez 
gives results of investigation of the rocks 
microscopically, which are illustrated upon a 
plate. Other chapters by Sanchez, Rangel and 
Castro discuss the more purely economic fea- 
tures, exploitation, drainage, machinery and 
metallurgical methods in such a way as to be 
serviceable to those for whose special advantage 
they were written. 
The volume is creditable alike to the authors 
and to the Minister of Internal Affairs, who has 
encouraged the expansion of the work. 
J. J. STEVENSON. 
Geologic Atlas of the United States, Folio 34. 
Buckhannon, West Virginia, 1897. 
This folio consists of a descriptive text, a 
topographic map, a sheet of areal geology, one 
of economic geology, one showing structure 
sections, and finally asheet giving a generalized 
section and table of synonymy. The authors 
are Joseph A. Taff and Alfred H. Brooks. 
The quadrangle comprises an area of 9314 
square miles and for the most part is located in 
the Appalachian coal field near the center of 
West Virginia, between latitudes 38°, 30’ and 
39° and longitudes 80° and 80°, 30’. It em- 
braces portions of Lewis, Upshur, Randolph, 
Webster, Braxton and Barber counties. The 
southeastern corner of the quadrangle lies in 
the district of parallel ridges which characterize 
the western border of the Great Valley, or cen- 
SCIENCE. 
[N.S. Vou. VI. No. 151. 
tral division of the Appalachian province. 
Rich and Mill, Back Fork, and Point moun- 
tains, which attain elevations or more than 4,- 
000 feet, are the principal border ridges here 
mapped. From these elevated ridges the sur- 
face, an inclined peneplain, falls away toward 
the northwest, down to an elevation of near 
1,700 feet. Six rivers have their sources within 
this quadrangle, West Fork of Monongahela, 
Buckhannon, Middle Fork, Valley, Little Kan- 
awha, and Elk, all belonging to the Ohio drain- 
age. These rivers, having their powers of cor- 
rasion augmented by the elevated and tilted 
surface of the country, have dissected the once 
nearly first country by deep, narrow channels. 
The stratigraphy column makes a section of 
about 4,600 feet of rock. Sixteen hundred feet 
of interstratified Devonian sandstone and shale 
are divided nearly equally between the Jen- 
nings and Hampshire formations. Of the Lower 
Carboniferous there are about 1,100 feet, of 
which less than 100 feet is Pocono sandstone; 
350 feet of Greenbrier limestone, and 650 feet of 
red shale, brown sandstone and conglomerate, 
making the Canaan formation. The remaining 
1,900 feet comprises the coal measures known 
in this folio as the Pickens sandstone, Pugh 
formation, Upshur sandstone and Braxton 
formation, which are composed of conglomer- 
ate, sandstone and shale with beds of coal. 
The structure of this district is typical of the 
two provinces which it includes. In the south- 
eastern portion, east of Rich Mountain, the 
structure is that of the folded region of Great 
Valley, which is characterized by long parallel 
anticlines and synclines with north-southwest 
axes. West of Rich Mountain the typical 
Cumberland Plateau structure prevails. Here 
the strata are slightly inclined and gently 
folded. 
The only product of economic importance is 
coal, of which there are seven workable beds. 
Two of these occur in the Pickens sandstone, 
three in the Upshur sandstone and two in the 
Braxton formation. The coals are from two to 
six feet thick. They have not been worked on 
a commercial scale, because other areas of pro- 
ductive coal lie between this field and the sea- 
board and nearer to large centers of coal con- 
sumption, both north and west. 
