Report issued by the U.S. Bureau of Mines detailing the laboratory-scale tests of the efficiency of the Trent process in cleaning coal, in which powdered coal, water, and oil is agitated or beaten together to remove impurities. The report includes details in tables detailing the efficiency varying the type and amounts of coal, oil, and water on the process.

This document reports the economic geology of the Lacasa area, Ranger district in North-Central Texas, with fieldwork done in April and May of 1919.

Booklet describing the biology of Alabama in two sections: (1) physiography and life zones, and (2) mammals. It also includes an annotated species list of mammals, bibliography, and index starting on page 81.

Report on recovering unburned fuel from boiler furnace refuse, based on processes used in Europe and tests in the United States.

Discussion of the updated rules in the third edition of the National Electrical Safety Code.

Memorandum presenting a description of the hydrodynamic lift theory of supporting services. This report is mainly about the task of finding suitable wing sections for given lift conditions. Formulas are given for lift magnitude and moment, which make it possible to obtain solutions of great simplicity and clearness.

The tests at the Gottingen laboratory included: friction tests on a surface treated with emaillite, verification tests on the M.V.A. 356 wing, and comparative tests of wing no. 36 at the Eiffel laboratory. The examination of all these experiments leads to the belief that, at large incidences, the speeds registered by the suction manometer of the testing chamber of the Eiffel laboratory wind tunnel are, owing to pressure drop, greater than the actual speeds. Therefore, the values of k(sub x) and k(sub y) measured at the Eiffel laboratory at large incidences are too low.

Report presenting a description of fluid compasses that are being used in aircraft, including why magnetic compasses are not usable. Details of the distant compass are provided, which is an improved form of the compass that has a practical application in seaplanes.

This report presents a method of calculating polar curves which is at least as precise as graphical methods, but it more rapid. Knowing the wind tunnel test of a wing and the performances of an airplane of the same profile, it is easy to verify the characteristic coefficients and, at the same time, the methods determining induced resistances.

This report presents a discussion of how to determine the location of a line or surface from experimental data. What we desire to know practically is the number of ordinates required to obtain a certain probable precision in drawing a line or surface.

"On April 15, 1920, the under Secretary of State for Aeronautics and Aerial Transport decided to adopt as Standard Atmosphere for official airplane tests in France, the atmosphere defined by the following law, known as the Law of the S.T.You.(Technical Section of Aeronautics): From 0 to 11,000 m. - 0=15-0.0065 Z and above 11,000 m. - 0= -56.5 degrees being the temperature in centigrade degrees at altitude Z expressed in meters. For altitude 0 the pressure is 760 mm of mercury. In the magazine "L'Aeronautique" Mr. A. Toussaint has already written at length on the first studies which led to the elaboration of this law. Since that time the results obtained have been confirmed by fuller and more abundant data which have justified the official adoption of the Law of the S.T.Ae" (p. 1).

A method is presented for soldering aluminum to other metals. The method adopted consists of a galvanic application to the surface of the light-metal parts to be soldered, of a layer of another metal, which, without reacting electrolytically on the aluminum, adheres strongly to the surface to which it is applied, and is, on the other hand, adapted to receive the soft solder. The metal found to meet the criteria best was iron.

Report describing the functions and operations of the United States Bureau of Commerce and its divisions during the fiscal year.

Technical paper issued by the Bureau of Mines over studies conducted on fire resistance on building columns. As stated in the introduction, "the purpose of this investigation is to ascertain (1) the ultimate resistance against fire, of protected and unprotected columns as used in the interior of buildings; (2) their resistance against impact and sudden cooling from hose streams when in a highly heated condition" (p. 12). This paper includes tables, illustrations.

Technical paper issued by the Bureau of Mines over quarry accidents reported during the year of 1919. The results of the accident reports collected are presented and discussed. This paper includes tables.

Technical paper issued by the Bureau of Mines over the development of gas masks designed for fighting fires. The characteristics of the different types of masks in development are presented. This paper includes tables, illustrations, and photographs.

Report issued by the Bureau of Mines covering petroleum laws of the U.S. and surrounding oil producing countries. As stated in the preface, "this bulletin includes the petroleum laws of (1) United States; (2) the several oil-producing States; (3) Canada; (4) Mexico; (5) the Republics of Central and South America" (p. iv).

Report issued by the U.S. Bureau of Mines on the characteristics and behavior of oil and coal distillation processes. The effectiveness of the distillation processes and the properties of the oil and coal mixtures are presented. This report includes tables, graphs, and illustrations.

Report discussing the the development of milling practice in Boulder County, the ore-dressing methods in use, and the local manufacture of ferrotungsten and tungstic oxide. Figures giving the production of tungsten concentrates in the Boulder district, in the United States, and in the world; data on the buying of tungsten ores; costs of production; and the normal tungsten requirements in this country are presented.

Note presenting a study of the influence exercised on the results of measurements by the dimensions and type of the tunnels used in aerodynamic laboratories, and on the comparison of the results with observations made in motionless and unlimited air.

From Summary: "This investigation was undertaken to determine whether the results obtained upon model tail surfaces can be used to accurately predict loads upon the full-sized tail; and also to find the distribution of load when large elevator angles are used, as the loads from such angles can not be obtained readily in free flight. The method consisted in using a metal horizontal tail surface inside of which small air passages, connecting with a series of holes in the surface, led the pressure off from the tail in rubber tubes. In this way the pressure at each of these holes was measured by a manometer at several angles of attack and several to the loading under similar conditions in the full-sized airplane and the manner of distribution is quite similar in the two cases when there is no slip stream."

This work was undertaken to obtain results on a small model of a complete airplane which might be used for comparison with corresponding tests made in full flight. Somewhat similar tests have been previously made at various other laboratories; but as certain discrepancies exist between corresponding tests in different tunnels, it has been deemed advisable to obtain a direct comparison for this particular installation. The present work covers tests on a one-twenty-fourth scale model at speeds varying from 6.7 m/sec. (15 m.p.h.) to 40.2 m/sec, (90 m.p.h.). A slip stream correction has been obtained by the use of a small belt-driven propeller mounted in front of the model, and force coefficients thus obtained are compared with the measurements of the same forces made in full flight on a geometrically similar airplane. This report gives lift, drag, and longitudinal moment values obtained in tests of a particularly accurate model over a wide range of speeds. A measure of the slip stream corrections on lift and drag forces was obtained by the use of a power-driven model propeller. Measurements were also made of forces and longitudinal moments for all angles from 0 degree to 360 degrees.

In this report a study is made of the effect on longitudinal and lateral oscillations of an airplane of simultaneous variations in two resistance derivatives while the remainder of the derivatives are constant. The results are represented by diagrams in which the two variable resistance derivatives are used as coordinates, and curves are plotted along which the modulus of decay of a long oscillation has a constant value. The same type of analysis is also carried out for the stability of the parachute.

This report, which is a continuation of the "Preliminary report on free flight testing" (report no. NACA-TR-70), presents a detailed theoretical analysis of statical stability with free and locked controls and also the results of many free flight test on several types of airplanes. In developing the theory of stability with locked controls an expression for pitching moment is derived in simple terms by considering the total moment as the sum of the moments due to wings and tail surface. This expression, when differentiated with respect to angle of incidence, enables an analysis to be made of the factors contributing to the pitching moment.