"Through the utilization of the "Magnus effect" on the Flettner rotor ship, the attention of the public has been directed to the underlying physical principle. It has been found that the Prandtl boundary-layer theory furnishes a satisfactory explanation of the observed phenomena. The present article deals with the prevention of this separation or detachment of the flow by drawing the boundary layer into the inside of a body through a slot or slots in its surface" (p. 1).

"Our attempts to improve the properties of airfoils by removing the boundary layer by suction, go back to 1922. The object of the suction is chiefly to prevent the detachment of the boundary layer from the surface of the airfoil. At large angles of attack, such detachment prevents the attainment of the great lift promised by the theory, besides greatly increasing the drag, especially of thick airfoils. This report gives results of those experiments" (p. 1).

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.

Report issued by the U.S. Bureau of Mines covering accidents that happened in metal mines located in the United States including statistics for injuries, fatalities, kinds and causes of accidents, and operational data, such as number of mine workers and shifts worked.

Report published by the U.S. Bureau of Mines which is a compilation of accidents in quarries located in the United States with data regarding the number and kinds of accidents as well as information about the mining operations (e.g., number of men employed, kinds of quarries, amount of work performed, etc.).

Report issued by the U.S. Bureau of Mines on the severity of accidents in the metal-mine industry. 34 metal-mines documented the number and severity of all accidents over the course if one calendar year. This report includes tables.

Report issued by the U.S. Bureau of Mines on the coal-mining related deaths in May, 1926. The 126 accidents are documented and categorized. The accidents are analyzed in order to prevent future accidents, and to implement safety procedures. This report includes tables.

"In order to apply profitably the mathematical methods of hydrodynamics to aeronautical problems, it is necessary to make simplifications in the physical conditions of the latter. In a valuable paper presented by Dr. Max M. Munk, of the National Advisory Committee for Aeronautics, Washington, to the Delft Conference in April, 1924, these necessary simplifying assumptions are discussed in detail. It is the purpose of the present paper to present in as simple a manner as possible some of the interesting results obtained by Dr. Munk's methods" (p. 93).

This article deals principally with Professor Bairstow's experiments on autorotation, in which the wing is free to rotate about an axis in its plane of symmetry, which axis is parallel with the direction of the wind.

Summary of physiography and life zones and mammals of North Dakota.

Experimental data, such as the results of tank tests of models, render it possible to predict, at least in principle, as to how a hull or float of a given shape will comport itself. We will see further along, however, how uncertain these methods are and how they leave room for empiricism, which will reign for a long time yet in seaplane research bureaus.

It seems desirable to have some simple method for calculating quickly and with sufficient accuracy: 1) the correct position of the center of gravity; 2) the requisite tail-group dimensions; 3) and the course of the wing and tail-group moments. In out deductions, we will first replace the biplane (disregarding the effect of stagger, decalage and induced drag) by an equivalent monoplane, whose dimensions and position in space can be approximately determined in a simple manner.

"The most usual method of arriving at the maximum amount of spindling or hollowing out permissible in the case of any particular spar section is by trial and error, a process which is apt to become laborious in the absence of good guessing - or luck. The following tables have been got out with the object of making it possible to arrive with certainty at a suitable section at the first attempt" (p. 1).

Technical paper issued by the Bureau of Mines over the Bowie-Gavin process. As stated in the introduction, "this paper describes a process and an apparatus designed to recover oil from such deposits" (p. 1). The results of experiments conducted using this process are discussed. This paper includes tables, illustrations, and photographs.

It was concluded that after the critical span or depth-breadth ratio has been reached, the modulus of rupture varies approximately inversely as the first power of the span and of the depth-breadth ratio. The direction of the lateral deflection is alternate between successive supports. For this reason, we believe that rib spacing along the spar is more important in reducing lateral deflection than the distance between supports at the strut points.

Three questions relating to the technical progress in the utilization of heavy oils are discussed. The first question considers solid injection in high-speed automobile engines, the second concerns the development of the hot-bulb engine, and the third question relates to the need for a more thorough investigation of the processes on which the formatation of combustible, rapidly-burning mixtures depend.

Three high-speed semi-diesel engines are examined through the use of indicator diagrams. Different fuel nozzles and fuels are investigated and conclusions are drawn.

A continuation of the discussion and overview of the present state of development of high-speed semi-diesel engines.

Report presenting an investigation to determine the effect of tubing length on the indicated pressure values as ascertained in the pressure distribution measurements on the PW-9. The purpose was to determine the percentage of error in the pressure readings which might be caused by various lengths of tubing between the pressure orifices and pressure cell at the manometer. The differences in head caused by variations in the length of tubing are small, the lowest recorded being zero, the highest 2.7 percent.

"There seems to be little reliable information conveniently available as to the resistance encountered by small spheres moving steadily at moderate speeds in fluids. The present paper, while presenting nothing new in the way of either theory or data, has three objects: first to show that published data are sufficient to furnish approximate information; second to present this information in form convenient for computation; and, third to indicate where further research is needed" (p. 1).

"A new trailing bomb-type instrument for photographically recording the flight-path angle and air speed of aircraft in unaccelerated flight is described. The instrument consists essentially of an inclinometer, air-speed meter and a film-drum case. The inclinometer carries an oil-damped pendulum which records optically the flight-path angle upon a rotating motor-driven film drum. The air-speed meter consists of a taut metal diaphragm of high natural frequency which is acted upon by the pressure difference of a Prandtl type Pitot-static tube" (p. 1).

This report presents methods by which the cells of large commercial airplanes may be reduced. The tail of large airplanes represent an area where considerable improvement in weight and size reduction can be attained.

Report issued by the Bureau of Mines over studies conducted on red iron-ore mining near Birmingham, Alabama. Results of the studies are presented and discussed, as are mining methods. This report includes tables, illustrations, and photographs.

This investigation was made for the purpose of determining the aerodynamic pressure distribution encountered on a "C" class airship in flight. It was conducted in two parts: (a) tests on the tail surfaces in which the pressures at 201 points were measured and (b) tests on the envelope in which 190 points were used, both tests being made under as nearly identical flight conditions as possible, so that the results could be combined and the pressure distribution over the entire airship obtained.