A. W. STICKNEY, the American geologist, reported captured by the Bolsheviki in Siberia is reported by the American consul at Harbin, in a message to the State Department, to be safe in the Altai District of Siberia.

WALTER HARVEY WEED has gone to Cuba.

C. H. Cook has resigned from the Canadian Geological Survey and has accepted a position as geologist for the Associated Gold Fields of Larder Lake.

CHESTER R. THOMAS is geologist for the Amerada Petroleum Corporation of Hulsa, Oklahoma, and in charge of their geologic work in Kansas.

EDWIN A. MCKANNA, formerly geologist with the Mexican Gulf Oil Co., is now with the International Petroleum Co., at Tampico, Mexico.

GEORGE E. BURTON, formerly with the Empire Gas & Fuel Co., has joined the geological staff of the East Butte Mining Co., with offices at Oklahoma City.

DR. HENRY ARTOWSKI, who is representing Polish mining interests in this country was in Washington recently.

A. W. LEHMANN, manager of the Catume Copper Co. in Chile, is making a tour of mining districts of the United States.

HARRISON & EATON, consulting geologists of Denver and Fort Worth, have recently completed an investigation of the oil and gas possibilities in western Oregon, conducted for the Oregon Bureau of Mines and Geology. A report on the results of this examination has been published.

H. LIPSON HANCOCK, general manager, Wallaroo Mining & Smelting Co., Ltd., has sailed for Sydney.

H. A. GUESS, of the A. S. & R. Co., has been in Utah recently visiting the company's properties there.

S. M. SOUPCOFF, mining engineer with the Utah Department of the A. S. & R. Co., has returned to Salt Lake City after an inspection trip to the Nacozari district, Mexico.

FRANK MERRICKS, mining engineer of London, has been elected president of the Institution of Mining and Metallurgy.

L. K. ARMSTRONG and John C. Semple have formed a partnership as consulting engineers, with offices at Spokane.

G. PERRY CRAWFORD, who has been making examinations in the Lordsburg, N. M., district, will sail about May 15 for London, to join a geological expedition to Spitzbergen.

HENRY W. TURNER, mining engineer, Mills Building, San Francisco, is making examinations in central Idaho.

JAY A. CARPENTER, mining engineer, has moved from Tonopah, Nev., to Los Angeles, Cal., where he will practice as consulting engineer at 1006 South Hill Street.

DR. FREDERICK G. COTTRELL has been nominated for director of the Bureau of Mines to succeed Van H. Manning, resigned.

THE UNIVERSITY OF ARIZONA through the Arizona Bureau of Mines is conducting an eight-week field course in geology and mining for advanced students in the Dos Cabezas Mountains in southeastern Arizona, to start July 1st. The region presents interesting geology, and ore deposits. Particulars may be secured from the director of the Arizona Bureau of Mines, University of Arizona, Tucson, Arizona.

THE TASMANIA GEOLOGICAL SURVEY has recently been reorganized and now includes more systematic investigations of ore deposits, underground water supplies, cement ceranine and paint materials, and the study of geologic conditions aflecting all government engineering undertakings. The publications issued are Bulletins, records, reports, mineral resources, water supply papers, and miners circulars. Dr. Loftus Hills is director, and A. M. Reid, P. B. Nye, and H. G. W. Reid are assistant geologists. W. D. Reid is in charge of the laboratory.

In the study of many problems of structural geology, graphic methods commonly yield results that are sufficiently accurate for the purposes at hand and they are therefore widely used. With the development of interest in more accurate results, however, it is necessary to turn to mathematical calculations and formulæ, and their use in applied geology appears to be increasing. Formulæ have the further advantage that they permit an analysis of the relative importance of each of the elements that enters into a problem.

The determination of the thickness of a group of superimposed 1 Published with the permission of the Director, U. S. Geological Survey.

beds is relatively simple where a vertical cross-section is well exposed. Where isolated exposures not too remote have similar strike and dip, the determination of the thickness of the beds is also simple. Where, however, isolated exposures have similar strike and different dip, the determination of the thickness of beds between them depends upon the assumptions that are made concerning their relations.

The general treatises on geology, such as those of Dana, A. Geikie, J. Geikie, Chamberlin and Salisbury, Pirsson and Schuchert, De Lapparent, Haug and Kayser only discuss the simplest conditions of inclined beds. Green2 presents an interesting discussion of the methods of determining thickness between outcrops that are parallel and normal to the line joining them, as well as the case where the outcrops are parallel, but oblique to the line joining them. Lahee3 discusses the conditions of folding, the construction of cross-sections and presents a table showing thickness between beds of similar dip, but does not discuss the case of different dip. Probably the method that is most widely used to calculate the thickness of beds between outcrops of different dip, is the graphic method described by Hayes. Another graphic method for the same conditions is based upon the assumption that the outcrops are parts of concentric beds (parallel folds). Both of these graphic methods are open to the objection that (1) they take undue time for accurate preparation, (2) they do not yield accurate results where the difference in dip is 5° or less, (3) they do not make proper use of the accurate data that are now generally available by the use of plane-table methods of surveying.

The widespread use of structure contour maps in the study of the structure of oil fields is placing considerable value on accuracy of the data needed to prepare them. In the study of the structural problems of a belt of folded rocks in Wyoming and the preparation of structure contour maps of the area, the writer found it desirable to develop formulæ for calculating the thick

2 Green, A. H., "Geology, Part 1, Physical Geology," 1882, pp. 460, 464–467. 3 Lahee, F. H., "Field Geology," New York, 1916, pp. 153-178, 405-417, 475. 4 Hayes, C. W., "Hand Book for Field Geologists," New York, 1909, pp. 31-32.

ness of a number of formations under many conditions of folding. The principle upon which the formulæ are based, is used in the second graphic method referred to above; that is, that the outcrops are parts of concentric arcs (parallel).

ELEMENTS IN THE MEASUREMENT OF FOLDED BEDS.

In order to insure uniform consideration of each problem that may arise, the thickness of a group of beds between two detached exposures or outcrops is defined as the perpendicular distance from the outcrop of the overlying bed to the downward projection of the underlying bed. Thus, in Fig. 43, the thickness of the beds between Bed B and Bed D is DJ.

The following elements enter into the calculation of the thickness of such a group of beds.

(a) The true dip of each of the exposures or their true inclination from the horizontal.

(b) The horizontal distance between the two exposures.

(c) The difference in elevations of the two exposures. (d) The assumption that may be made concerning the manner by which the beds were deformed or folded from the horizontal position, for this assumption determines the method that should be used in projecting the underlying bed downward.

(a) The True Dip of the Beds.-In the determination of the true dip of any bed it is first necessary that it be clearly observable, and this, as all geologists know, is not always the case. Many stratified rocks show minor laminations that diverge considerably from the surface of stratification and even these are locally so rough that their trend cannot be determined accurately. In many places, it is impossible to obtain good natural exposures but it is interesting to record that many companies exploring for oil now find it profitable to undertake considerable exploration to lay bare good surfaces of stratification, from which to interpret the local structures.

In considering thick masses of some varieties of sedimentary rocks, the question may arise whether the lower stratum actually persists to a point under the higher stratum with the same char