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THE increasing speed of modern aircraft has brought to the forefront the necessity for making a careful drag analysis of all aircraft in order to separate out the essential drag, that is to say the drag that is unavoidable, from the non‐essential drag. Most designers, we believe, now do this in order to see what progress is being made in the streamlining of their products. By this means we are enabled to see the relative importance of the drag terms and to arrive at a figure of merit. The ideally‐streamline aeroplane, though not at present a precise proposition, is like other ideals unattainable. It is the standard to which designers may aspire, but which they cannot achieve.

I WISH to thank the President and the Royal Society of Italy for the honour they have conferred by inviting me to read this paper before the 5th Volta Congress as part of a discussion on high speeds in aviation. The contributions which General Crocco has made to this subject have been valuable and stimulating. In the present paper the general question of high airscrew tip speeds is considered and the results obtained from model airscrew tests are reviewed.

Studies on the impact of tourism in art cities underlined that many cities begun to suffer too many costs because of mass tourism. The problem of costs/benefits balance was in some case further complicated by the quick increase in a peculiar kind of excursionists — the so called false excursionists. Their increase is in fact joined with the spreading around the city of “alternative” accommodations. But false excursionists bring to the destination more costs and less benefits than traditional tourism, as a relevant part of their budget is spent where they are lodging. Thus, this sort of tourism “development” calls for visitors management policies able to reduce costs and maximize the tourism benefits for the city. But these policies require a deep understanding of the relationship between demand and accommodation supply, and between accommodations within and outside the city. And, more important, a continuous monitoring on how these relationships change in time, and why. Pricing and product strategies put into effect by accommodations, joined with changes in the demand behaviour, are in fact the basic variables of a mechanisms that might eventually lead to a substantial increase in false excursionists number and a stagnation in overnight tourists demand, with major consequences on the cost/benefits ratio for the art city as a whole. Aim of this paper is to introduce a set of 10 indicators and, through their application on the Venice situation, show how they can be used to analyze on diachronic terms the impact of accommodation evolution on demand choice.

The forces on ellipsoidal bodies placed obliquely in a converging or a diverging stream can be found direct by calculation of the pressures on the surfaces. It seemed worth while to do this in illustration of the general question, as a rather plausible line of argument had led to erroneous values of the transverse force. The results are found to agree with those of the indirect, but more general, investigation by Professor G. I. Taylor in R. & M. 1166.

Microstructure noise contaminates high-frequency estimates of asset price volatility. Recent work has determined a preferred sampling frequency under the assumption that the properties of noise are constant. Given the sampling frequency, the high-frequency observations are given equal weight. While convenient, constant weights are not necessarily efficient. We use the Kalman filter to derive more efficient weights, for any given sampling frequency. We demonstrate the efficacy of the procedure through an extensive simulation exercise, showing that our filter compares favorably to more traditional methods.

NEW COUNCIL The Council for the year 1948/49 is as follows:

IT is shown in the present paper that a beam may be constructed, consisting of a steel section securely bolted to a lower section of high‐tensile aluminium alloy, having a weight much lower than that of a plain steel beam of equal strength. This is frequently desirable when the weight of a steel beam would be excessive, but the cost of a section constructed entirely of aluminium alloy is unwarranted.

“IN the event of war, electrical equipment will be reduced to a minimum and all radio will be removed from aircraft in order to carry more ammunition or an extra bomb.” What the reader's reactions are to that quotation, I do not know, but what I do know is that it is typical of remarks made by people of importance in the aircraft industry before 1939.

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

Automobile and Aircraft Engines. By A. W. Judge, A.R.C.S., A.M.I.A.E. (Second Edition) [Pitman 42s. net.] The ground covered by the original edition of this book was so wide that it should have proved of great value, both to the engineer and to the student.