The navigational problem. In order to find out how an aircraft is tracking with respect to the ground, we can either obtain information from data accurately placed with respect to the ground, or assess the horizontal movement of the air masses through which the aircraft is flying and combine this motion with that of the aircraft through the air. To determine the track we require accurate knowledge of the aircraft's heading and of the drift, which is the effect of the beam component of the wind. Along any given course line the navigator can make a series of drift observations, usually visual and therefore requiring downward visibility, and estimate the departure from the course line by averaging such observations to obtain the integrated effect of the drift. Since the sole purpose of drift observation is to estimate the departure of an aircraft from a given course line, a method of obtaining this total departure from a single observation or pair of observations, under any visibility conditions, is of considerable value. Again, if it is possible to estimate before flight the total integrated effect of drift for the whole flight, and our object is merely to fly to reach our destination, then the necessity of taking drifts during flight will be obviated.

At 2215 hours GMT on 21 September 1947 the U.S.A.A.F. All-Weather Flying Centre's Automatic C54 took off automatically from Stephenville, Newfoundland, and twelve hours and five minutes later landed at Brize Norton, England. Neither pilot nor navigator had interfered with the automatic equipment during the entire flight. What, briefly, is the navigation equipment and procedure employed on such a flight?

Equipment. The navigation equipment consists of three magnetic heading selectors, two air log units or AMUS and a radio compass which will automatically switch to a number of preselected frequencies.

Some apology, or at least an adequate excuse, is needed for resurrecting a theoretical treatment of the effect of coriolis acceleration on observations of altitude made with a bubble sextant. Such an excuse is provided by the recent publication by Dr. J. J. Green of an article suggesting that the correction table (Z-correction) given in both the British and American Air Almanacs (and in many other Air Almanacs) is incomplete. In a reasoned letter to the Editor of Navigation, Dr. G. M. Clemence, Director of the American Nautical Almanac Office, has given a simple and straightforward explanation of the two separate and distinct causes for the deviation of the zenith as indicated by the bubble of a bubble sextant; and he has further justified the present practice adopted in the almanacs. Considerable interest has, however, been aroused and it seems opportune to give a previously unpublished general derivation of the theoretical correction, together with a brief discussion of the difficulties of practical application.

Why the perfect air map does not exist. Air maps have been struggling for years to reach perfection; most of them fall far short of it for three main reasons:

(1) Maps are designed by highly skilled specialists who, however, do not generally know from first hand experience what the practical requirements are. They rely on hearing of these from practical airmen.

(2) The better the practical men are at map reading the less able they are to put into words how they set about it and what is required for the ideal air map.

(3) Map production is extremely expensive in time, work and materials with the result that map makers are loath to scrap a map once made, if it will ‘do,’ even though they realise it might be improved.

Pressure pattern flying embraces a number of air navigation techniques all of which have one common feature: they relate pressure distribution along an aircraft's flight path to that component of the wind which acts at right angles to the aircraft's heading. My intention is to give a brief outline of the theory underlying these techniques.

Wind is brought about by horizontal pressure differences in the earth's atmosphere. Air tends to move from an area of high pressure towards an area of low pressure under the influence of the pressure gradient force. The direction of its motion is, however, affected by the earth's rotation in space. Considering this rotation in the horizontal plane only, it is at a maximum at the poles and zero at a point on the equator. At any intermediate point of latitude ϕ, the speed of rotation in the horizontal plane is proportional to the sine of the latitude. In the northern hemisphere the rotation is anticlockwise; in the southern hemisphere it is clockwise with reference to outer space.

In my book The Theory and Applications of Harmonic Integrals (hereinafter referred to as H. I.), Chapter iv is devoted to the application of the theory to algebraic varieties. In order to introduce harmonic integrals on an algebraic variety I have to assign a metric to the variety; this metric is not related to the variety in any invariant sense, and indeed its introduction is extremely artificial. Nevertheless it turns out that we can deduce from the properties of the harmonic integrals a number of properties of the variety which are birationally invariant, that is, do not depend on the choice of metric. This remarkable fact seems to indicate either that the invariant properties in question should be obtainable directly without the introduction of the harmonic integrals, or that the metric introduced is not so artificial as it first appeared to be. This note is intended to examine this question.

At the first International Meeting on Radio-Aids to Marine Navigation held in London in May 1946 some 105 delegates of twenty-three maritime nations met to discuss and witness demonstrations of some of the remarkable advances made in radio-navigation during the war and to consider the progress made in relation to their peacetime uses for marine transport.

At the invitation of the U.S. government a second meeting was held a year later, in New York and New London, to show the progress made in America, to illustrate, with demonstrations, the U.S. policy and to pave the way to international standardisation. The U.K. delegation was led by Sir Robert Watson-Watt.

1. In this paper we find explicitly the base for the prime ideal associated with any irreducible Vd−1 on a Segre variety, or a Veronesean variety, Vd. This work extends that of an earlier paper (1) in which the base was found when the Vd−1 is a complete intersection of Vd with one primal. As particular examples we can write down the base for any irreducible curve on a quadric surface, a Veronese surface or a Del Pezzo surface. We also show how the base for any prime ideal changes under a Veronesean transformation.

British south american airways have recently been carrying out a series of tests on flight refuelling. The first of these tests took place over southern England and were carried out on a scheduled basis at various heights both by day and by night and all proved successful—with the exception of two which were cancelled on account of bad weather, that is, bad weather on the ground and not in the air. The second part of the series has now taken place and consisted of London-Bermuda-London return nights on a weekly basis for a period of three months.

The process of flight refuelling does not in fact involve any particular navigational problem, but rather the simple problem of ‘approach’. The aircraft admittedly must intercept, but thanks to the fact that various devices are used for the actual approach of one aircraft to the other the navigational accuracy required for the interception is not at the moment of a very high order.

Equipment has been designed and constructed for the interruption of the ion beam in a high-voltage accelerating tube and for the detection and measurement of the period of short-lived radioactive elements. This method has been applied to the measurement of the half-life of 12B which has been found to be 27 ± 2 msec. The reaction 15N(n, α)12B has been detected.

In this paper an approximate formula is developed for the phase shifts required in the calculation of the scattering of particles according to wave mechanics. It is shown to be more accurate than the current approximations and it is not difficult to handle. The same method can also be used to compute any quantity which is sensitive to the form of the wave function near the centre of force (e.g. a matrix element).

The foundation of the Institute of Navigation has given satisfaction to many, but perhaps to none more than the shade of the great man who in 1673 inaugurated on the basis of the old charitable institution of Christ's Hospital ‘a nursery of children to be educated in Mathematics for the particular use and service of navigation’. That science has made some strides since Samuel Pepys's day. But no one who has read Arthur Bryant's fascinating study of the Great Secretary of the Admiralty under the Restoration can doubt that old Samuel would have been well abreast, if not ahead, of all developments, especially as they affected the King's Fighting Services. His comments on the subject after his experience of the Great Storm of 1684 have a very realistic and modern ring about them: ‘We are very solicitous in our disputes and opinions touching our draughts and log lines and things’ he wrote ‘when we are at a loss for our ways … but as soon as ever we see land all difference is forgot, or any desire of recording the truth, but on the contrary, everybody endeavours to make himself be thought to have been in the right, and not thinking also that they should ever come to the same loss in the same place again. Hence it comes that the science of navigation lies so long without more improvement’. How true, and how curious that it should have been more than 260 years before the foundation of this Institute, under a president one of whose predecessors was called in by Pepys in 1686 to defend against unjust criticism a treatise on the science of navigation.

The yields of 139Ba per fission in natural uranium by unslowed neutrons from a mixed radium-beryllium source and by C-group neutrons were compared. In each case the fission rates measured with an ionization chamber were correlated with the β-ray activity of 139Ba, chemically extracted from a mass of uranium oxide exposed to an identical neutron spectrum. The ratio of the two fission yields is found to be 0·84 ± 0·03. The possibility of using 139Ba as a local or integrating indicator of fission in extended uraniferous media, and of distinguishing between the contributions by fast neutrons and by slow neutrons is discussed.

During the past few years, several methods for the measurement of fast neutron flux have been developed in the Cavendish Laboratory. A critical inter-comparison is given in a forthcoming paper by Allen, Livesey and Wilkinson. Some of the methods depend on the counting of protons which are projected by the neutrons from a film of hydrogen-rich material. Polythene is usually employed because its hydrogen content is high and accurately known. If the thickness of the film is comparable with the range of the fastest proton produced by the incident neutrons, it becomes necessary to know the range-energy relation for protons in polythene. This is particularly so in the ‘thick film chamber’ method to be described by Allen and Wilkinson. Another method, the ‘homogeneous ionization chamber’ method to be described by Bretscher and French makes use of the well-known principle that the average density of ionization obtaining in a chamber whose walls have an atomic composition identical with that of the gas which fills the chamber is the same as that in an infinite extent of that gas. This principle itself depends on the identity of mass stopping power of solid and gas of the same atomic composition. The chamber usually used has polythene walls and is filled with ethylene.

The mariner has for many years been able to procure charts for practically any waterway in the world and in most cases has the selection of a variety of scales to suit his purposes. The air navigator has not been so happily placed.

Shortly after the end of the 1914–18 war the nations subscribing to the International Convention to Air Navigation agreed the need for world cover in aeronautical charts at various scales, but, up to the commencement of the last war, the 1:10,000,000 basic map, for which the French government accepted responsibility, was the only series to reach completion. Various areas were also charted at scales of. 1:1,000,000 and larger.