90 BIBLIOGRAPHY AND INDEX OF N. A. GEOLOGY, [bull. 149. 
715 Ward (Lester F.). Ago of the Island series. 
Science, newser., vol. iv, pp. 757-760, 1896. 
Discusses the age of certain strata of the Atlantic Coastal plain, 
assigned by Professor Marsh to the Jurassic. 
71G Washington (Henry S.). The magniatic alteration of hornblende 
and biotite. 
Jour, of Geol., vol. iv, pp. 257-282, 1896. 
Reviews the theories concerning the alteration of hornblende and 
biotite as due to the resorptivo action of a magma, describes the condi- 
tions under which the phenomena takes place, and discusses the author's 
proposed hypothesis and the origin of some augite andesites. 
717 Webster (Clement L.). Notes on the geology of southwestern 
New Mexico. 
Am. Geol., vol.xviii, pp. 56-57 (correspondence), 1896. 
Describes the general features of the Carboniferous and Cretaceous 
formations of the region. 
718 Weed (Walter Harvey). Sedimentary rocks [Yellowstone Na- 
tional Park folio, Wyoming]. 
U. S. Geol. Surv., Geol. Atlas of U. S., folio No. 30, 1896. 
Describes the character and distribution of the Algonkian, Cambrian, 
►Silurian, Devonian, Carboniferous, Juratrias, Cretacer us, Tertiary, and 
Pleistocene formations and the hot spring deposits. 
719 — — The Fort Union formation. 
Am. Geol., vol. xviii, pp. 201-211, 1896. 
Reviews the early descriptions of the Fort Union group, and of the 
Laramie and the Livingston beds, gives two sections of Fort Union strata 
in Montana, and discusses the differences of the physical and faunal 
characters of the Laramie and Fort Union beds, and the evidences indi- 
cating that the Fort Union, as originally described, includes strata of 
distinct and separate formations. 
720 Ore deposits of the Little Eocky Mountains, Montana. 
Eng. and Mg. Jour., vol. lxi, pp. 423-424, 1896. 
Describes the geologic features of the region and the occurrence and 
character of the gold ores. 
721 Mineral resources of the Judith Mountains, Montana. 
Eng. and Mg. Jour., vol. lxi, pp. 496-498, 1896. 
Describes the geology of the region and the occurrence of gold. 
722 Notes on the geology of theNeihart mining district, Montana. 
Mining, vol. i, pp. 25-29, 1896. 
Describes the geologic structure of the region, the character of the 
igneus rocks, and the occurrence of the precious metals. 
723 and Pirsson (Louis V.). Geology of the Castle Mountain 
mining district, Montana. 
U. S. Geol. Surv., Bull. No. 139, 164 pp., 17 pis., 1896. 
Describes the geologic structure, the lithologic character of the Algon- 
kian, Cambrian, Silurian, Devonian, Carboniferous, Juratrias, Creta- 
ceous, and Miocene rocks and the petrographic characters of the igneous 
rocks. Includes notes on the glacial geology, on the occurrence of the 
precious metals and copper, and on the minerals collected. 
