In endeavouring to present a paper on the relative problems of supercharging aircraft and motor-car power units, the author wishes to convey at the outset that no attempt is being made to give a scientific investigation of air compression, but rather to review the present stage of supercharger development, the difficulties which have to be met by the engine designer in applying such a device to a high-speed petrol engine, and with the hope of stimulating from this review a discussion on the possible advantages to be obtained thereby.

For the purpose of this paper, supercharging an internal combustion engine may be defined as :–The filling of the cylinder during each cycle by mechanical means in the form of a pump, with a greater amount of charge than would be possible with natural aspiration.

In the tragedy of R38 it is the structural failure which happens to have attracted most attention. The tragic consequences which resulted from the structural failure were fatal almost solely because of fire.

The nature and causes of the structural failure are now well known, and in the science and art of hull design sufficient progress has been made to render future structural failure as improbable in an airship as in a ship at sea. It is fitting, therefore, that a large proportion of the essays submitted for the R38 Prize should describe work which has been done to eliminate the initial cause of failure.

Of all the treasures accumulated by the Society in the course of its long career, in some ways the most interesting is the oil painting depicting a river scene with a balloon overhead, which hangs in the Secretary's room. In spite of this I have never seen any account of it, and all trace of the means by which it came into the Society's possession seems now to be lost–unless by chance this note may catch the eve of someone still living who has knowledge of the facts. At first sight it seems to be merely one of the many fanciful pictures of a balloon ascent so common at the end of the XVIIIth century in the period immediately following the invention of the balloon, but some years ago I stumbled, more or less by accident, on certain facts that lift it out of the ruck. When I was, in 1924, collecting the material for my book, Aeronautical Prints and Draivinys, I came across an engraved portrait of Joseph Michel, the elder Montgolfier, joint inventor of the balloon.