From Introduction: "This bulletin is the sixth in the series of petroleum bibliographies published by the Bureau of Mines, Bulletins 149, 165, 180, 189, and 216 being compilations for the years 1915, 1916, 1917, 1918, and 1919-20 respectively. In this bulletin the same general plan has been followed in arranging the references, but one or two additions have been made in the classification."

From Introduction: "The Bureau of Mines since its establishment has always taken an active interest in the utilization of lignite and in the development of the lignite deposits of the United States. Extensive lignite fields occur in the west central States, notably in North Dakota, Montana, Wyoming, Colorado, and Texas; there are smaller areas in several other Sates, some of which are widely separated."

From Introduction: "This bulletin presents the results of 36 tests made on a 468-horse-power Edge Moor boiler fired with pulverized coal at the Oneida Street Station of the Milwaukee Electric Railway & Light Co., Milwaukee, Wis."

From Introduction: "This bulletin aims ti bring the salient features of the process to the attention of metallurgists for the purpose of furnishing information to and receiving comments from interested parties with the ultimate hope that the process will be a commercial success."

From Introduction: "This chapter indicates the methods of determining several of the alloy metals when occurring together in the same sample. Most materials seldom contain more than two or three of these elements, but considerable time may be saved if determinations can be combined. Details of the analyses and separations are not given here, as they have been covered more fully in other chapters. Whenever possible, reference is made to the particular chapter. Only sufficient directions have been given to outline the method of procedure, actual conditions for the separations being presented on other pages."

Part one of a bulletin from the U.S. Bureau of Mines discussing oil and gas field waste prevention, and policies on field operation. According to the introduction, "Part I of this manual points out types of oil and gas wastes and suggest, in detail or by reference, the most practical and effective methods in current practice for stopping these wastes. Throughout Part I the department's operating policy is given, with interpretations of the 'Operating Regulations' for enforcing every practical measure of conservation" (p. 1).

From Introduction: "The analyses given in this bulletin are of samples of delivered coal. This bulletin gives the results of analyses of samples delivered coal collected from July 1, 1915 to January 1, 1922."

From Scope of the Work and Findings: "The work was divided into two parts, namely, field work and laboratory investigations. The most interesting and important of the laboratory investigations. The most interesting and important of the laboratory findings were: (1) The presence of hydrogen sulphide (H2S) in the gases and vapors from light Mexican crude; (2) the extreme toxicity of H2S; (3) the absence of arsine, stibine, phosgene, hydrocyanic acid, and other toxic substances; (4) treatment recommended for poisoning by H2S; (5) use and limitations of oxygen breathing apparatus, hose masks, and gas masks."

From Introduction: "In the following pages the writer has endeavored to give an account of the many methods, advantages, and disadvantages of preparing and burning powdered coal."

Part two of a bulletin from the U.S. Bureau of Mines discussing oil and gas field waste prevention, and policies on field operation. According to the introduction (from part 1), "Part II comprises the revised 'Operating Regulations' which supersede all previous regulations and will govern future operations on public lands" (p. 1).

From Introduction: "The officials of the North Butte mine we engage in making a study of ventilation problems before the coming of the investigators, so that opportunity was given to work with those officials for several months. This bulletin is a result of studies made from the data collected during the two and one-half years of study and observation above outlined."

Report presenting an investigation of problems related to helicopters. Also included are the history of the evolution of the helicopter and a series of propeller experiments.

N.A.C.A. has developed an instrument which makes a continuous record of the angular position of the control surfaces of an airplane, not only in steady flight but during acrobatics as well. It has proven useful in researches into stability and controllability, and from records obtained from it many otherwise obscure details of piloting technique have been available for the instruction of pilots, from novices to seasoned experts.

"Tests were carried out in the small wind tunnel of the Gottingen establishment on a complete model of the AEG D I airplane. The agreement between the model and the complete airplane applies particularly to the wings, which have ribs cut out of sheet metal and built up in exactly the same manner as in the actual airplane. Various series of tests were carried out with this model in which one or the other of the control surfaces were adjusted to various angles, while the others remained in their neutral positions" (p. 1).

"The conventional airplane strut fails by buckling. The first signs of failure usually are compression cracks on the concave side of bending. It would therefore appear that if an initial tension could be introduced in the outside fibers, this tension would have to be relieved before the compression load could make itself felt" (p. 1).

"For a first approximation the air flow around the airship hull is assumed to obey the laws of perfect (i.e. free from viscosity) incompressible fluid. The flow is further assumed to be free from vortices (or rotational motion of the fluid). These assumptions lead to very great simplifications of the formulae used but necessarily imply an imperfect picture of the actual conditions. The value of the results depends therefore upon the magnitude of the forces produced by the disturbances in the flow caused by viscosity with the consequent production of vortices in the fluid" (p. 1).

"The airflow about a model while being tested is often sufficiently affected by the model support to lead to erroneous conclusions unless appropriate corrections are used. In this paper some new material on the subject is presented, together with a review of the airfoil support corrections used in several other laboratories" (p. 1).

The following article shows that the phenomena of climbing flight can be determined with sufficient accuracy and represented very clearly, for all flight positions, by means of the thrust diagrams. This method has often given good results.

"The vertical distribution of the pressure, temperature, and density of the atmosphere varies from day to day. Thus, rates of climb on different days cannot be compared directly, but must be corrected with reference to a standard rate of diminution of air density with increasing altitude. The following problem, therefore, has to be solved" (p. 1).

In the first series of wind tunnel tests, the drag and cross wing force of all the struts were measured at a wind speed of 30 mph and at angles of yaw from 0 degrees to 20 degrees. To determine the magnitude of the VL effect, each strut was tested at zero yaw and at a series of speeds ranging from 15 to 38 mph. Although designed as fairings for cables, part of these sections gave such high crosswind forces that they seemed to have possibilities as airfoils.

Note presenting some comparative performances of new types of airplanes under the same conditions. The airplanes were compared with some that are already in use and give an accurate idea of the progress shown in the new types.

Note presenting some information on the effect of changes in the loading and in the disposition of the supporting framework on the covering fabric. The magnitude of the air forces to be taken into account and the corresponding factors of safety to be expected will be covered in a future report. Tables regarding some of these fabric characteristics are provided.

"For the calculation of the parasite resistance of an airplane, a knowledge of the resistance of the individual structural and accessory parts is necessary. The most reliable basis for this is given by tests with actual airplane parts at airspeeds which occur in practice. The data given here relate to the landing gear of a Siemanms-Schuckert DI airplane; the landing gear of a 'Luftfahrzeug-Gesellschaft' airplane (type Roland Dlla); landing gear of a 'Flugzeugbau Friedrichshafen' G airplane; a machine gun, and the exhaust manifold of a 269 HP engine" (p. 1).

"These regulations, approved by the Under Secretary of State for Aeronautics, in a ministerial decree 1124/2a, Feb. 19, 1923, cancels the regulations of Aug. 31, 1920, and supplements the decree of Aug. 14, 1920, fixing the conditions under which certificates of airworthiness may be issued,in conformity with Article 5 of said decree" (p. 1).