80 BIBLIOGRAPHY AND INDEX OF N. A. GEOLOGY, [bull. 146. 
520 Watts (W. L.). The gas and petroleum yielding formations of 
the Central Valley of California. 
Cal. State Mg. Bureau, Bull. No. 3, 100 pp. 
Describes the occurrence of natural gas, petroleum, and asphaltum in 
this region and gives the sections of several wells and lists of the fossils 
collected in Cretaceous and Tertiary strata. 
521 Weed (Waiter Harvey). Montana coal fields. 
U. S. Geol. Surv., 16th Ann. Kept., part iv, pp, 144-146. 
Notes on the occurrence of coal in the Cretaceous rocks of Montana 
in a paper by E. W. Parker on the production of coal in 1894. 
522 and Pirsson (Louis V.). Highwood Mountains of Montana. 
Geol. Soc. Am., Bull., vol. vi, pp. 389-422, pis. 24-26. 
Describes the topographic features, geologic structure, and the 
characteristics of each eruptive center of the Highwood Mountains. 
Describes the remarkable differentiation zone of Square Butte, and the 
characters and minerals of the dark rock, for whieh the name "shonki- 
nite " is proposed. 
523 On the igneons rocks of the Sweet Grass Hills, Montana. 
Am. Jour. Sci., 3d ser., vol. J, pp. 309-313. 
Describes the topographic character and geologic structure of the 
Three Buttes, known as the Sweet Grass Hills. Describes the petro- 
graphic characters of the igneous rocks, quartz-diorite porphyrite, 
quartz-syenite porphyry, and minette occurring in this region. 
524 Igneous rocks of Yogo-Peak, Montana. 
Am. Jour. Sci., 3d ser., vol. 1, pp. 467-479. 
Describes the topographic character and geologic structure of the 
Little and Big Belt mountains, Yogo Peak forming a conspicuous sum- 
mit of the Little Belt range. Describes the petrographic character of 
the syenite, yogoite, and shonkinite, illustrating the variation and 
gradation in the chemical and mineralogic composition of the Yogo rocks. 
Discusses the differentiation at Yogo Peak and the classification adopted. 
525 Weeks (Joseph D.). Manganese. 
U. S. Geol. Surv., 16th Ann. Kept., part iii, pp. 389-457. 
Includes a brief discussion of the origin and occurrence of manganese 
and notes on its occurrence in Alabama, Arkansas, California, Colorado, 
Georgia, Indian Territory, New Jersey, Pennsylvania, Tennessee, Ver- 
mont, Virginia, New Brunswick, Nova Scotia, and Cuba. 
526 Natural gas in 1894. 
U. S. Geol. Surv., 16th Ann. Rept., part iv, pp. 405-429. 
Includes notes on the occurrence of natural gas in Ohio, Indiana, and 
California. 
527 The Elk Garden and Upper Potomac coal fields of West Vir- 
ginia. 
Am. Inst. Mg. Engrs., Trans., vol. xxiv, pp. 351-364, figs. 1-2. 
Gives a general description of the region and tables of chemical 
analyses of the coal and of coal production. 
528 Weidman (Sainuel). On the quartz keratophyre and associated 
rocks of the north range of the Baraboo Bluff's [Wisconsin]. 
Univ. of Wis., Science ser., vol. i, pp. 35-56, pis. 1-3. 
Gives a geologic map of the region and describes the areal geology and 
the occurrence and microscopic characters of the quartz keratophyre. 
