MARYLAND GEOLOGICAL SURVEY 307

Structural Material.

Mineral Resources U. S., 1888, Washington, 1890.

Statistics of the granite industry for 1888. pp. 536, 538; marble, p. 541; slate, p. 541;
cement, p. 551; lime, p. 555; brick, pp. 560, 566. See also p. 526.

EMMONS, S. F. Notes on the Gold-Deposits of Montgomery
County, Maryland.

Trans. Amer. Inst. Min. Eng., vol. xviii, 1890, pp. 391-411.

Geological occurrence of the gold ores with an account of mining operations since
1867. Suggestions regarding the best methods of economical development of the deposits.

HOBBS, W. H. Ueber die Yerwachsung von Allanit (Orthit) und
Epidot in Gesteinen.

Tschermak's min. u. pet. Mitth., vol. xi, 1890, pp. 1-6.

———— On some metamorphosed eruptives in the crystalline rocks
of Maryland.

Trans. Wis. Acad. Sci., vol. viii, 1890, pp. 156-160.

Discussion of the metamorphism of gabbro to hornblende gneiss. Illustrations taken
from the vicinity of Baltimore and Ilchester.

HOLMES, W. H. A Quarry workshop of the flaked stone imple-
ment makers in the District of Columbia.

Amer. Anth., vol. iii, 1890, pp. 1-26.

Gives a section through the Potomac gravels on Piney Run and a photograph of the
" head " of a 44 foot trench.

———— Excavations in an Ancient Soapstone Quarry in the Dis-
trict of Columbia.

Amer. Anth., vol. iii, 1890, pp. 321-330.

Gives a few facts on the geological occurrence of the quarries and describes the pro-
ducts of the quarrymen.

KEYES, CHARLES ROLLIN. Discovery of fossils in the limestone of
Frederick Co., Maryland.

Johns Hopkins Univ. Cir. No. 84, vol. x, 1890, p. 32.

Gives a geological section and description of Frederick valley and enumerates the
fossils found there.

KUNZ, GEO. F. Gems and Precious Stones of North America. 4to.
Scientific Pub. Co., New York, 1890. [2nd edit. 1892.]

MACFARLANE, J. R. An American Geological Railway Guide.
2nd edit. 8vo, 426 pp. Appleton, 1890.

Maryland notes based on data from Uhler, Williams, Fontaine and Chester.

PATTERSON, HARRY J. Report of the Chemist.
2nd Ann. Rept. Md. Agri. Exper. Sta. College Park, 1890, pp. 67-94.
Remarks on the composition of marls and soils from Maryland with many analyses,
pp. 79-87.