Report presenting the Bureau of Mines' investigation into acid processes of extracting alumina. The paper discusses the sulphuric acid processes and other work with hydrochloric and nitric acids so that the comparative advantages can be appreciated.

This report contains the aerodynamic properties of the wing sections U.S.A. 5, U.S.A. 27, U.S.A. 35 A, U.S.A. 35 B, Clark Y, R.A.F. 15, and Gottingen 387, as determined at various Reynolds numbers up to an approximately full scale value in the variable density wind tunnel of the National Advisory Committee for Aeronautics. It is shown that the characteristics of the wings investigated are affected greatly and in a somewhat erratic manner by variation of the Reynolds number. In general there is a small increase in maximum lift and an appreciable decrease in drag at all lifts.

Report discussing the air forces on a systematic series of biplane and triplane cellule models which are measured in the atmospheric density tunnel.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the president, congressional report, summaries of the committee's activities and research accomplished, bibliographies, and financial report.

"The significance attaching to "column effect" in airplane wing spars has been increasingly realized with the passage of time, but exact computations of the corrections to bending moment curves resulting from the existence of end loads are frequently omitted because of the additional labor involved in an analysis by rigorously correct methods. The present report represents an attempt to provide for approximate column effect corrections that can be graphically or otherwise expressed so as to be applied with a minimum of labor. Curves are plotted giving approximate values of the correction factors for single and two bay trusses of varying proportions and with various relationships between axial and lateral loads" (p. 485).

This report presents the results of an investigation of the planing and get-away characteristics of three representative types of seaplanes, namely, single float, boat, and twin float. The experiments carried out on the single float and boat types have been reported on previously. This report covers the investigation conducted on the twin-float seaplane, the DT-2, and includes as an appendix, a brief summary of the results obtained on all three tests. At low-water speeds, 20 to 30 miles per hour, the seaplane trims by the stern and has a high resistance. Above these speeds the longitudinal control becomes increasingly effective until, with corresponding speeds of 56 to 46 miles per hour. It was further determined that an increase in the load caused little if any change in the water speed at which the maximum angle and resistance occurred, but that it did produce an increase in the maximum angle.

From Introduction and Summary: "This bulletin describes the third series of coal-dust explosion tests by the Bureau of Mines in its experimental mine and covers a period from 1919 to the end of 1924, inclusive. A few related tests made in 1925 are also included."

Report compiled by the U.S. Bureau of Mines including statistics on fatalities in coal mines located in the United States as well as data regarding the various operations (e.g., number of miners employed and average production). The information is organized into tables for comparison and the text draws some overall conclusions in the summary.

The Amiot 120 B 3 is designed as a French combat aircraft. It can accept a variety of engines, and is equipped with 2 machine guns as well as specialized bomb sights and other combat equipment.

Report issued by the Bureau of Standards discussing the comparison of American, British, and German metal fit standards. The comparisons between national standards of the three countries are presented and described. This report includes tables, and illustrations.

"This investigation, which is a continuation of Technical Report 154, follows very closely the earlier methods and covers a number of service airplanes, whereas the previous report covered but one, the JN-4H. In addition to the air speed, acceleration, and control positions as given in report no. 154, information is here given regarding the distance run and the ground speed for the various airplanes during the two maneuvers" (p. 457).

"The extensive use of magnesium and its alloys in aircraft has been seriously handicapped by the uncertainties surrounding their resistance to corrosion. This problem has been given intense study by the American Magnesium Corporation and at the request of the Subcommittee on Materials for Aircraft of the National Advisory Committee for Aeronautics this report was prepared on the corrosion of magnesium" (p. 419).

"This report describes the 5-inch bore by 7-inch stroke single cylinder test engine used at the Langley Field Laboratory of the National Advisory Committee for Aeronautics in laboratory research on internal-combustion engine problems and presents some results of tests made therewith. The engine is arranged for variation over wide ranges, of the compression ratio and lift and timing of both inlet and exhaust valves while the engine is in operation. Provision is also made for the connection of a number of auxiliaries" (p. 469).

Different methods of determining the size of fuel droplets in the atomization process are presented. The distribution of those drops is also presented in graphic form.

Technical paper issued by the Bureau of Mines over mining of red iron ores in Birmingham, Alabama. As stated in the introduction, "the present paper deals more specifically with the development and handling of ore as affected by folds and faults in the ore bed, and considers changes that may be desirable or necessary in future mining practices" (p. 2). This paper includes illustrations, and photographs.

"This report describes tests made to obtain direct measurements of engine power in flight. Tests were made with a Bendemann hub dynamometer installed on a modified DH-4 Airplane, Liberty 12 Engine, to determine the suitability of this apparatus. This dynamometer unit, which was designed specially for use with a liberty 12 engine, is a special propeller hub in which is incorporated a system of pistons and cylinders interposed between the propeller and the engine crankshaft. The torque and thrust forces are balanced by fluid pressures, which are recorded by instruments in the cockpit" (p. 505).

"This report describes tests made for the purpose of determining the distribution of pressure over a model of the tapered portion of the upper wing and the aileron of a Fokker D-VII Airplane. Normal pressures were measured simultaneously at 74 points distributed over the wing and aileron. Tests were made throughout the useful range of angles of attack with aileron setting ranging from -20 degrees to +20 degrees. The results are presented graphically" (p. 541).

From Introduction: "The drilling and blasting practices described in this bulletin are chiefly those in use at the time of these visits. Information, obtained by correspondence, on recent changes at certain mines is also included. The bulletin is confined to descriptions and comparisons of drilling and blasting methods at the six open-cut mines."

The D.B. 10 is manufactured of duraluminum and special high resistance steel. It can be used as a passenger aircraft or as a bomber. Details of the design, wings, fuselage, empennage, engines, landing gear, characteristics, performances, drawings, and photographs are provided.

This report was prepared at the request of the National Advisory Committee for Aeronautics in order to supply a systematic study of the relations between the flight velocity V and its horizontal component V subscript H, in power glides. Curves of V and V subscript H plotted against the inclination of the flight path 0 are given, together with curves which show the maximum values of V subscript H and the corresponding values of 0. Curves are also given showing the effect of small departures from the horizontal in high speed performance testing.

From Summary: "This paper reports the results of an extensive program of measurements on 11 ignition systems differing widely in type. The results serve primarily to give representative data on the electric and magnetic constants of such systems, and on the secondary voltage produced by them under various conditions of speed, timing, shunting resistance, etc. They also serve to confirm certain of the theoretical formulas which have been proposed to connect the performance of such systems with their electrical constants, and to indicate the extent to which certain simplified model circuits duplicate the performance of the actual apparatus."

Report issued by the Bureau of Mines over studies conducted on the ferric sulphate-sulphuric acid process. As stated in the introduction, "the work reported here comprises merely a study of the chemistry of the process and the mechanical conditions that would have to be observed in practice" (p. 1). This report includes tables, and illustrations.

Introduction: "This bulletin abstracts and reviews essential details of reports on 59 fires in different coal mines in the United States, describes the circumstances of origin and the methods of controlling or extinguishing the fires, and points out the lessons taught."

This report gives the pressure distribution and resistance found by theory and experiment for simple quadrics fixed in an infinite uniform stream of practically incompressible fluid. The experimental values pertain to air and some liquids, especially water; the theoretical refer sometimes to perfect, again to viscid fluids. For the cases treated the concordance of theory and measurement is so close as to make a resume of results desirable. Incidentally formulas for the velocity at all points of the flow field are given, some being new forms for ready use derived in a previous paper. (author).