I went to sail with the Arabs after selling the ship Joseph Conrad, which had proved too expensive for a private citizen to continue to run indefinitely as his own school-ship. I had always wanted to see something of Arab navigation because they were the pioneers. Semitic navigators and mathematicians were among the experts gathered by Prince Henry the Navigator at the school at Sagres, in Portugal, and the dhow voyages of the western Indian Ocean were very old. But I found that today the Arab dhow-captains do not ‘navigate’, as such: they apply personal knowledge to coasting passages, even though the passages cover some thousands of miles. For example, in a big double-ended dhow of the type known as a boom, from Kuwait, I sailed some 8000 miles in about eight months—down the east coast of Africa with the favouring north-east monsoon, as far almost as the monsoon blew, and then back again up the coast in the transitional period between the monsoons.

That a ship's captain may exercise supreme powers when at sea has been recognized since maritime laws were first formulated. But when Francis Drake summarily executed Thomas Doughty in Patagonia in 1578 there were serious misgivings at home, and the commanding officer of the next long distance expedition was hedged about with carefully thought out restrictions, and ordered, save ia the last resort, to bring any serious offender home as a prisoner. This voyage was organized and financed by the Earl of Leicester, Drake and a number of City merchants, its objective being to open up trade with the Far East by a voyage round the Cape. It had originally been intended to put Martin Frobisher in command, but for reasons unknown a gentleman and soldier of fortune, who had been with him on the second and third voyages to the Northwest Passage, Captain Edward Fenton, was substituted for Frobisher. This caused murmuring among the sailors who evidently thought poorly of him. And he did indeed turn out a weak, vacillating leader, though full of his own importance, so that the voyage was a failure, and two of his ships actually left him.

The growing complexity and variety of navigator techniques and equipment, associated with a marked increase in aircraft speed, necessitates a more detailed investigation of the navigator's task. Despite an increase in the range and automaticity of navigational aids, the demands made upon him are changing their character, and are in danger of being excessively high.

A detailed recording of navigator activity in flight seems the only practical approach to this problem. The knowledge gained by such a task analysis would be expected to furnish information on the following aspects:

(a) Objective evidence of fatigue effects.

(b) The effects of experience on the navigator's work pattern.

(c) The need, if any, for the modification of training methods.

(d) Equipment layout and design in relation to efficiency.

(e) Practical specification of the navigator's layout.

(f) Indications of specific situations which may with advantage be subjected to laboratory investigation.

In the early days of civil aviation, aircraft flew too low to encounter jetstreams. Later they were no doubt encountered, when aircraft were flying at medium heights of from 10,000–20,000 ft.; however, the infrequency of astro fixing in those days would generally disguise a high-velocity wind by meaning it with low-velocity winds, producing resultant winds of medium velocity. Occasionally, however, very high winds would be experienced and the unexplained displacement of position would be attributed to a navigational error or some other cause of that nature.

A novel instrument for use in chartwork has been devised combining a ruler with the principle of the square Douglas protractor, and permitting immediate indication of direction to be read without ambiguity. A prototype of this instrument, which will probably be known as the Harries Course and Bearing Indicator, is illustrated in Fig. 1. It is constructed of Perspex, and the basic ruler component has engraved upon it a long double-ended arrow, emphasized as the line AA in the illustration. Centrally pivoted above this arrow is an approximately rectangular ‘aligning plate’, B, on which are engraved equally-spaced lines, C, parallel to the 180°/360°, or north /south, line of a circular compass rose.

To obtain the direction of a course laid off on a chart, the bevelled edge, D, of the ruler is placed along it. The aligning plate is then rotated until the north/ south lines on it are seen to be parallel to any adjacent meridians (Fig. 2). The true course can then be read off directly from that degree of the compass rose lying directly over the appropriate arrow head—an action which can be carried out on a folded map or chart held on the knee.

The pilot or navigator expects the forecaster to supply him with: (a) forecasts of wind and temperature; and (b) forecasts of meteorological hazards, e.g. turbulence, icing. The increase of operating height and range of modern aircraft make it increasingly difficult to maintain a high standard of accuracy of forecasts.

Almost all the long-range civil transport aircraft entering service during the next few years will be equipped with some form of instrument system. It is proposed to describe here some aspects of the developments which have been embodied in one such system, the Smiths Flight System, and to indicate its scope when applied to the operation of such aircraft.

Since the war the operation of a high-performance transport aircraft on congested and competitive routes has become an increasingly complicated process. With the advent of the gas turbine, cruising speeds have doubled, and at the same time there has been a tendency towards higher standards of economy and safety. The development of the air traffic control system has brought about a demand for greater precision in navigation, and in the most congested areas by far the greatest number of flights are conducted under instrument conditions. Meanwhile, aircraft have also become more complex, and the pilots themselves are often expected to monitor the operation of the controls and instrumentation associated with the engines, electrics and pressurization as well as carry out the navigation. This extra work has had to be undertaken without any relaxation of the general vigilance which constitutes good airmanship.

This paper, which gives a useful description of the procedures used by one transatlantic operator, was presented in Montreal at a meeting of the Canadian Institute of Navigation held on 7 December 1955. Many of the methods discussed are referred to in the preceding three papers.

1. Any discussion of today's long-range navigational practices and problems seems to lead inevitably to pressure-pattern and jet-stream flying. The reason might well be that during recent years the more important practical developments appear to have concerned techniques rather than aids or instruments.

Thomas Hariot's recently discovered manuscript ‘The Doctrine of Nauticall Triangles Compendious’ was the subject of a paper in this Journal by Professor Taylor and D. H. Sadler which poses but leaves unanswered the intriguing question of the method he employed in his computation. Sadler shows that the method depends on the fact that if sequences of meridional parts are in arithmetic progression the corresponding values of tan (45° − ½φ) will be in geometric progression. This is at once obvious from the modern formula for meridional parts:

But how did Hariot, writing before 1596, discover the relationship when neither logarithms nor the integral calculus had yet been invented; and was he able to prove it? It is the purpose of the present paper to supply a proof which requires neither logarithms nor the calculus. It is not claimed that this was necessarily the method that Hariot employed, although the manuscript reveals several points of similarity.

Two problems concerned with the use of radar to reduce the risk of collision are frequently called to mind by reports of casualties and correspondence relating to them. One is that of avoiding the ‘region of collision’ and the other is how best to proceed within such a region when it is unavoidable. The writer's attention was recently drawn to that phrase as it was used in 1932 in the judgment of the Court of Appeal on the collision between Haliotis and Chisone. The phrase caught the eye because of the need (in the writer's view) of a striking term to appeal to the imagination of some incautious mariners and impress them with the undesirability in fog of leaving too much to chance; it seemed to have more significance than the term ‘close-quarter situation’.

In the case in question the Chisone was found partly to blame because she did not stop her engines until five minutes after hearing the fog signal of the Haliotis. Although she was stopped, or nearly so, some minutes before the collision, she had come directly into the path of the Haliotis and so was considered to have committed the breach of Art. 16 (Rule 16 (b)) ‘in the region of the collision.’

During the last few years much has been learned about the navigational developments and techniques of the English pioneers of colonization in the New World. This has been made possible in some measure by the formation in America of a private library of the books relating to the art of navigation as practised by the Elizabethan and early Stuart seamen. It was in the course of forming his remarkable collection of early Americana that Mr. Henry C. Taylor of New York, purchased copies of Captain John Smith's An Accidence or The Pathway to Experience. Necessary for all Young Sea-men, or those that are desirous to goe to Sea … first published in London in 1626, and A Sea Grammar, with The Plaine Exposition of Smiths Accidence for Young Sea-men, enlarged … first published in London in 1627, subsequent editions of this latter work being entitled The Sea-mans Grammar, etc.

In the contribution under this heading to the Forum (Vol. IX, p. 348) Fig. 1 of Mr. P. G. Powell's note was misplaced. The figure results from the table given at the foot of p. 351 and indicates the approximation in the overall distribution to normal Gaussian laws.

Announcement. As from the editions for the year 1958 the Abridged Nautical Almanac and the American Nautical Almanac will become identical in content, and will be reproduced from identical material, apart from the title pages and covers; they will for the time being retain their present titles, and will continue to be printed and published separately in the United Kingdom and the United States. The unified Almanac will be produced jointly by H.M. Nautical Almanac Office of the Royal Greenwich Observatory, Herstmonceux, and the Nautical Almanac Office of the U.S. Naval Observatory in Washington, to meet the general requirements for surface navigation in the two countries.

Unification became a possibility with the decision to prepare copy for the Abridged Nautical Almanac on the card-controlled typewriter in H.M. Nautical Almanac Office; this machine is identical with that at the U.S. Naval Observatory, which has been used to prepare copy for the American Nautical Almanac since 1950. A large number of arrangements were tried for the daily pages, some with one day to the page or two days to the opening, and others with three days to the opening. The consensus of opinion in the United Kingdom favoured the latter form, which is already in use in the American Nautical Almanac. This opened the way to a detailed investigation into an arrangement that would prove acceptable to users and producers in both countries. The unified Almanac is the result of this collaboration.

Impatience is frequently expressed at the slow rate of progress in improving the efficiency of air traffic control. It is being expressed most forcibly at this time in the United States, because the military services require the separation problem to be solved for the large numbers of military jet flights, and because civil jet aeroplanes have been ordered by the airlines and will soon appear on the Federal Airways. Although a great deal of basic study has been made of the problem of air traffic control, it is becoming clear that there is no panacea for its solution. Air traffic control is concerned with the safe expeditious flow of air traffic. This involves a number of separate but interrelated problems both in the aircraft and on the ground. Thus we see a programme of development on a very wide front involving navigation aids, communications, radar performance and presentation, data display and so on. Progress in any one field may affect the requirements in another, and so it is most necessary for all concerned to have a clear view of the situation as a whole in order that they may see the wood as well as the trees. Lively discussion of the subject can therefore be most fruitful, both among those directly concerned—the pilots and the controllers—and among the specialists in the various branches of development.

Summary of a paper presented at a meeting of the Auschuss für Funkortung at Essen on 28 February 1956.

In any investigation of the accuracy of Decca fixes it is necessary to distinguish between systematic and random errors. Investigations are generally based on a comparison between a Decca fix and a fix obtained by some other method; because of the high accuracy of Decca the other method must in practice be a terrestrial fix. The investigation can be made by comparing the decometer readings with values calculated for the true position; or the Decca position may be compared directly with the true position. The first way gives the differences of the Decca observations in terms of percentages of a lane, and the second shows immediately the errors of the Decca fix. The second method includes the uncertainty caused by the siting of the Decca stations, that is by the angle of intersection of the Decca hyperbolae. The second method will be of more direct use to practical navigators while on the first will be based considerations of a theoretical and strictly technical nature.

The history of navigation and hydrography, as of other crafts or ‘mechanick arts’, has to be constructed from very imperfect materials. Instruments and charts, as the tools of practical men, were commonly discarded when they were worn out or superseded. The high mortality among original charts makes generalization in the comparative history of cartography hazardous. That no Portuguese charts before 1500 are now known does not allow us to conclude that none was made but only that none has survived. Many of the early charts that have been preserved are decorative examples drawn for royal or other patrons; those by which pilots conned their ships had a smaller expectation of life and are correspondingly rare.