316 BIBLIOGRAPHY AND CARTOGRAPHY

Prepared by the local committee of the Amer. Inst. Min. Eng., Baltimore,
1892.

Includes data on various industries and the following papers: 1. Geology of the
Crystalline Rocks, by G. H. Williams. 2. Physiography of the Region and Geology of
the Sedimentary rocks, by N. H. Darton. This book is accompanied by a preliminary
edition of the Baltimore sheet of the U. S. G. S.

———— The Volcanic Rocks of South Mountain in Pennsylvania
and Maryland.

Amer. Jour. Sci., 3rd ser., vol. xliv, 1892, pp. 482-496, map, plate x, figs. 1-8.

Scientific Amer. Supplement, July, 1893.

(Abst.) Amer. Natl., vol. xxvii, 1893, p. 273 (W. S. E.).
J. H. U. Cir. No. 103, vol. xi, 1893, pp. 45-47.

First identification of volcanic rocks in the Appalachians. The paper embodies
many facts collected by Dr. Williams and by Miss Florence Bascom, upon which are
based the general conclusions that the rocks are not sedimentary, as previously con-
sidered, but devitrifled surface eruptives.

———— The University and its Natural Environment.
Johns Hopkins Univ. Cir. No. 96, vol. xi, 1892, pp. 54-56.
Uses Maryland as an Illustration.

WILLIAMS, G. H., and CLARK, WM. B. Report on short excursions
made by the Geological Department of the University during the
autumn of 1891.

Johns Hopkins Univ. Cir. No. 95, vol. xi, 1892, pp. 37-39.

Describes various areas about Baltimore and Washington.

1893.

ANON. General Mining News—Maryland.
Eng. and Min. Jour., vol. lvi, 1893, p. 404.
Kaolin discovered near Northeast, Maryland.

BABB, CYRUS C. The Sediment of the Potomac River.

Science, vol. xxi, 1893, p. 342.

Contains Interesting data concerning the sediments transported.

BASCOM, F. The Structures, Origin and Nomenclature of the Acid
Volcanic Rocks of South Mountain.

Jour. Geol., vol. i, 1893, pp. 813-832.

Shows that the " quartz porphyries " were Identical with modern volcanics, but
have since been modified by devitrification. Such an alteration is indicated by the
prefix " apo."

BIRKINBINE, JOHN. Iron Ores.

Mineral Resources U. S., 1891, Washington, 1893.

Brief references to the " brown ores " with a few statistics, pp. 12-27.