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Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Committee, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued.

AN equation of state is derived for a system consisting of a perfect gas containing solid particles in suspension. It is assumed that temperature‐equilibrium is maintained throughout. The results are applied to calculate the kinetic energy obtainable from the adiabatic expansion of a stream of such a system, and related quantities. The assumptions of the treatment are critically examined.

THE graphical methods of one‐dimensional gas dynamics are reviewed and developed to obtain a complete representation of adiabatic flow of perfect gases in ducts of constant cross‐section. The dimensionless charts, from which the variation of the state of the gas along the duct axis can be determined, are analysed and the methods of their construction given. The form of the charts depends only on the value of the ratio of specific heats.

THE calculation of gas turbine efficiencies on the basis of the real properties of the working medium is a laborious process. Such a calculation involves the determination of the composition of the combustion gases for a series of air/fuel ratios, and the evaluation of a number of thermodynamic properties at various temperatures and pressures, such as the enthalpy (total heat), entropy, specific heats, etc. These properties are calculated from the tabulated properties for the component gases with the aid of the rules for mixtures.

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued

Under this heading are published regularly abstracts of all Reports and Memoranda of the Aeronautical Research Council, Reports and Technical Notes of the United States National Advisory Committee for Aeronautics and publications of other similar Research Bodies as issued

THE IMPORTANCE OF DILUTION FOR TURBO‐JETS The S.R.A. 1 turbo‐jet engine is of the ducted‐fan‐type. This arrangement seemed the best at the time when the problem (of good performance) was presented, and the results obtained have since confirmed the original expectations. Most other turbo‐jets, however, if not all, are now of the undivided‐flow type.

This is an excellent book. Coming as it does from the pen of a scientist who is also an experienced teacher it fulfils all that the author set out to accomplish. Of the existing books on Thermodynamics comparatively few have succeeded in presenting the subject in so attractive and palatable a fashion—attractive because the art of the true teacher illumines and embellishes the whole work and palatable because, while the average engineering student has very often viewed the study of thermodynamics as a form of forced labour due to the wrong approach, Dr Schmidt, who was Professor of Thermodynamics in the Engineering University of Brunswick, succeeds from the outset in focusing the reader's attention and whetting his curiosity. He then proceeds so to build up the fundamentals as to make the deeper theories and their application, which are so ably handled later in the book, a revelation of clarity and development.

WHEN evaluating engine efficiencies, mean effective pressures or the work done by the piston in internal combustion engines or compressors, it is generally assumed that the state of the working fluid is uniform throughout its mass. From this it follows that the expression for work where P denotes pressure and V, volume, holds. Now, it is known that, strictly speaking, this expression applies only in the limiting case of zero piston velocity, when the motion of the piston, and the thermodynamic process in the cylinder are said to be quasi‐static. The question, therefore, poses itself as to how far such an assumption is justified, when applied to a modern high‐speed reciprocating engine, say, an aircraft or motorcar engine, when piston velocities of the order of 40 ft./sec. are encountered.