IV ADVEKTISEMENT. 
PP 28. The superior analyses of igneous rocks from Roth's Tabellen, 1869 to 1884, arranged according |j 
to the quantitative system of classification, by H. S. Washington. 1904. 68 pp. 
B 239. Rock cleavage, by C. K. Leith. 1904. 216 pp., 27 pis. 
B 241. Experiments on schistosity and slaty cleavage, by G. F. Becker. 1904. 34 pp., 7 pis. 
B 253. Comparison of a wet and crucible-fire methods for the assay of gold telluride ores, with notes 
on the errors occurring in the operations of fire assay and parting, by W. F. Hillebrand and 
E. T. Allen. 1905. 33 pp. 
B. 261. Preliminary report of the operations of the coal-testing plant of the United States Geological 
Survey at the Louisiana Purchase Exposition, St. Louis, Mo., 1904; E. W. Parker, J. A. Holmes, 
M. R. Campbell, committee in charge. 1905. 172 pp. 
Correspondence should be addressed to — 
The Director, 
United States Geological Survey, 
February, 1905. Washington, D. C. 
