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IN the early part of 1926, tests were carried out in the N. P. L. wind tunnels upon models of high‐speed seaplanes for the Schneider Trophy‐Competition in America. Owing to lack of time it was decided not to enter British machines for that contest, but the wind tunnel work was continued, as the Air Ministry wished to further the development of high‐speed craft. After the 1926 contest the Air Ministry decided to allow R.A.F. seaplanes to be entered by the Royal Aero Club, and to assist the Club in the competition in the following year. The high‐speed seaplane work was, therefore, again applied to machines for the Schneider Trophy Contest.

IN order to obtain machines of large carrying capacity, there is a tendency to increase the number of power units, and it is of great interest to consider the effect of this policy upon safety in flight. It is obvious that, if all the power units are of the same construction, the possibility of failure of one engine in a machine fitted with two engines is twice that in a machine fitted with one engine, so that in general the probability of one unit going out of action in a multi‐engined machine is proportional to the number of power units employed. In the case of a single‐engined machine horizontal flight cannot be maintained after the engine fails, and unless the failure occurs in the vicinity of a safe landing ground disaster may result. In the case of a multi‐engined machine, however, if level flight can be maintained on the power obtainable from the remaining units, it may bo possible to arrive at a safe landing ground without further trouble. The question, therefore, arises as to which factor is the more important, the increase in the probability of failure, or the ability to fly level with an engine out of action.

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

It must be difficult for many to contemplate the numerous changes in progress and projected without wondering why it all has to happen now. Of course, there have always been with us those who would change everything, even those who would spoil; all seemingly unable to leave anything alone; unwillingly to let us be for what we are. Then there are those who dislike change of any kind in their familiar environment and strangely, children are the most conservative of us all, and others who do not object to change when it is necessary, but only when it is change merely for the sake of change. The changeover to the metric system, or to use one of the grating terms of the new technological language, metrication, must be accepted as a natural sequence to decimal currency and advances in industry. A revolution in weights and measures, it will indeed present very great problems throughout the country and at all levels, which will dwarf those presented by the switch to decimal coinage, for at worst, these may be just confusing to the general public and a price‐raiser in small‐value commodities, despite assurances to the contrary.

WE wish our readers success and prosperity for 1935. In the pages of our last number was given a brief retrospect of the events of 1934, and there is no advantage in repeating any part of it. Suffice to say, the year was one of the most memorable in the annals of libraries from the point of view of the new buildings which have been erected to serve great places. The year before us will present a full programme of work for all librarians. The major interest will probably be the conference to be held at Manchester in September, when hundreds of librarians will have the opportunity of seeing the building of the largest of British, if not of European, public libraries. We understand, too, that the conference will deal systematically with the efficient library in the modern community, but no doubt fuller information upon this programme will be forthcoming very shortly. The time is not ripe, we fear, for us to expect anything in the shape of a consolidating library aft which shall bring into coherency the scattered library laws of this country. We hope something will be done in the year to improve the examination system of the Library Association, which fails to give satisfaction as it stands at present. We confidently expect that the co‐operation embodied in the Regional Library Bureau will be extended, and as our recent pages have shown, we hope that the National Central Library will be relieved of some of its financial anxieties by direct action upon the part of public libraries and of the Treasury. There are signs that the country is gradually returning to prosperity, and we hope that in any such event libraries will benefit and librarians will receive some attention in the matter of their salaries.

AS far as the author is aware, no attempt has yet been made, either on the experimental or on the theoretical side, to extend to three dimensions the conceptions regarding the formation of a vortex street in the wake of a body, as developed by Karman and Rubach for two dimensions. The problem is complicated by the fact that owing to experimental difficulties there is an almost complete absence of direct visual evidence regarding the nature of the flow in the wake of a three‐dimensional body. This makes it extremely difficult to construct, in imagination, the possible vortex configuration that might originate. It should be understood, therefore, at this stage, that until such direct evidence is available, the suggestions put forward here are to be regarded as merely of a tentative nature, but this has not prevented mathematical investigation on the basis of these suggestions from proceeding.

THE outstanding property of the biplane to be described, as determined from model tests, is stability in roll up to angles of incidence in excess of 40 deg. (Fig. 8). This is achieved without any additional mechanism or parts, simply by the form and disposition of the wings. Maximum lift is slightly increased (Fig. 6) and there are minor advantages as regards coming in to land, aileron control and spinning.

IT has been found by model tests that the lift of a combination of an aeroplane body and a wing is not in general equal to the sum of the lifts of the two components when tested separately. This difference is broadly referred to as an interference effect. It is dependent on a number of factors which can be generalised into three groups:—

AN attempt is made here to summarize the present state of the theory of wind tunnel wall interference in a form that will be of some value to those using wind tunnels. The type of wind tunnel work frequently carried out without a complete knowledge of the corrections is also mentioned as it is of interest to those asking for, and using, wind tunnel results. A list of the most useful published reports on the subject is given at the end of the article, it is, however, by no means a complete guide to the literature of the subject, much of which is contained in academic volumes not usually available to the engineer using a wind tunnel.

Under this heading will be 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.—Ed,