The choice of airspeed and altitude have a far more critical effect on economy of operation throughout the flight of turbo-jet aircraft than with the piston-engined type. The method of operating piston-engined aircraft for maximum range is well known, though it is normally only used on very long stages when fuel is critical; generally constant-power or constant-airspeed cruising, which result in a small penalty of fuel or payload, are preferred. The choice of operating height is also fairly wide within certain obvious limits. With jet aircraft, however, airspeed and operating height become critical and variations from economic operation reduce the payload or range considerably. The preparation of the flight plan, involving the choice of cruising altitude and speed, therefore becomes of major importance to the jet operator and navigator. The guidance of the aircraft's flight path in the vertical plane, in other words, takes on a new significance and affects the navigator's task both in planning and in flight.

Aircraft such as the Comet normally fly above cloud formations, but their approach to the airport involves a long and more or less gradual descent which may take them through adverse weather conditions. Violent thunderstorms, for example, which are fairly common in some parts of the tropics, constitute an obvious danger, and the provision at airports of an effective system of cloud warning could provide an added measure of safety along air routes.

The new U.S. Hydrographic Office publication H.O. 249, Sight Reduction Tables for Air Navigation, comprises three volumes: Volume I covers all latitudes and contains tables of altitude and azimuth of selected navigational stars; Volume II contains tables of computed altitude and azimuth angle for latitudes 0°–39°, declinations 0°–29°; and Volume III contains tables of computed altitude and azimuth angle for latitudes 40°–89°, declinations 0°–29°. The tables have been produced jointly by the American Nautical Almanac Office and H.M. Nautical Almanac Office for the U.S. Hydrographic Office. The British edition of the tables is being published by H.M. Stationery Office as A.P. (Air Publication) 3270; the actual tables are identical with the American edition but the introductory matter has been reset.

During the last half-century authors who have had occasion to write about the history of the magnetic compass have quoted extensively from The Intellectual Rise in Electricity, by Park Benjamin (New York, 1895). The wealth of references given by this writer to substantiate his statements promises a reliability which is at times sadly lacking. In one part of this book the statement is made that: ‘A single Finnish Compass has been discovered for which the people claim great antiquity, the card or scale of which is marked for a latitude where the sunrise and sunset at the summer and winter solstices differ by sixty degrees.’ For this the author gives as authority Nouvelles Annales des Voyages, Vol. xvii, page 414 (Paris, 1823), but in fact this reference contains no suggestion of the discovery of an ancient Finnish compass. All there is, is a brief reference to the ancient Finnish method of dividing the compass card which, instead of four cardinal points, had six, spaced sixty degrees apart. This information was said to be based on an article in a monthly miscellany, published in Finland under the name of Mnemosyne. Captain D. Daragan of Helsinki has been kind enough to obtain for me a copy of the original article, which was printed in Swedish, and Rektor S. Nydell has been so good as to translate it into English.

More research into fuel reserve policy needs to be done if airlines are to achieve the finest balance between payload and safety. Progress is required in the accuracy of weather forecasting, in streamlining the techniques associated with the choice of required fuel reserves, and in research into the greater benefits that could be derived from well-developed operational control policies, exploiting to the full the enormous potentialities of a system-wide communications network. Captain Moline has suggested some of the inadequacies of present-day techniques.

Since the publication in 1951 of a paper read to the Institute on bird navigation, a number of significant advances have been made in this field and a brief review of such progress will not be out of place. Most of this recent work has been concerned with the ability of birds to home to an area previously known to them. A useful summary, in English, has been published on the experiments done in Germany on the simple, inherited, one-direction movements of young birds on their first migration. The use of the Sun as a compass, in at least many cases, appears to be well established.

The use of radar for preventing collisions at sea seems to have raised four main problems in applying the International Regulations for Preventing Collisions at Sea. These are: (I) In what, if any, measure radar contact covers ‘sighting’ within the meaning of Article 28; (2) whether the position of another vessel can be ascertained by radar in the precise sense intended in para. 2 of Article 16; (3) how, if at all, the use of radar should be considered to modify the ‘existing circumstances and conditions’ which, under Article 16, govern the use of moderate speed in poor visibility; (4) the application of the Steering Rules (Articles 17–27) when radar is in use.

It has hitherto been generally presumed that the division of the horizon into thirty-two points was a development of the late medieval period. Such a division, it has been said, was impossible in the pre-compass era. ‘It is questionable whether even so many as sixteen directions could have been picked out and followed at sea so long as Sun and star, however intimately known, were the only guides’, one eminent authority has declared; ‘Even the sailors in the north-western waters had only four names until a comparatively late date.’ Chaucer's reference in his Treatise on the Astrolabe to the thirty-two ‘partiez’ of the ‘orisonte’ has for long been quoted as the earliest evidence on the subject. The Konungs Skuggsjà, a thirteenth-century Norwegian work, however, refers to the Sun revolving through eight œttir; and the fourteenthcentury Icelandic Rímbegla talks of sixteen points or directions. An important discovery by the distinguished Danish archaeologist, Dr. C. L. Vebæk, in the summer of 1951, brings a new light to the whole problem and makes the earlier held view scarcely tenable. Vebæk was then working on the site of the Benedictine nunnery (mentioned by Îvar Bárdarson in the mid-fourteenth century) which stands on the site of a still older Norse homestead on the Siglufjörd, in southern Greenland. Buried in a heap of rubbish under the floor in one of the living-rooms, together with a number of broken tools of wood and iron (some of them with the owner's name inscribed on them in runes) was a remarkable fragment of carved oak which evidently once formed part of a bearingdial. This was a damaged oaken disk which, according to the archaeologists, dates back to about the year 1200.

The usual method of conducting ships’ speed trials is for the ship to make runs over a measured mile. Recently, however, sea trials have been carried out using other methods, which seem to offer certain advantages. The trials of the S.S. United States, for example, were carried out using Raydist and Decca was used in the speed trials of S.S. Manchester Spinner off the Isle of Man. This paper discusses various methods of determining the ship's speed, the diameter of the turning circle and other data normally measured during sea trials, and makes an assessment of their relative convenience and accuracy.

During the course of recent hydrographic and oceanographical investigations in the Pacific, H.M.S. Challenger made considerable use of the extensive Loran coverage now provided by the United States. This marine radio position-fixing aid was particularly useful in the west Pacific in the area between Japan and New Guinea where the coverage of ground-waves is considerable. In this article an attempt is made to describe some of the work for which Loran was used, the principles on which it was used, and the accuracy expected and errors obtained. No attempt has been made to describe the operation of the system, which has been adequately covered in this Journal and in numerous other publications.