In the course of a survey of the Arafura Sea by H.M.A.S. Barcoo, many astronomical observations were made under good, and controlled, conditions; through the courtesy of the Admiralty these observations have been made available for analysis. This analysis has been regarded as a pilot investigation for the working party on the accuracy of astronomical observations at sea. Its main, crude, result gives (from these observations) a standard deviation of a single observation as 1.1.

During the latter half of 1952, H.M.A.S Barcoo was engaged in surveying an area, 200 miles by 30, in the Arafura Sea some 50 miles north-west of Cape Wessel. Seven fleets of beacons were laid out, each consisting of about 14 beacons at intervals of about 5 miles. The first beacon of each fleet was used as a datum beacon and its position determined by astronomical observations by three observers, both morning and evening on two days; each observer took as many stars as possible on each occasion and the mean of three or four shots of each star. The datum beacons were connected by taut-wire runs and it was found that the taut-wire distances were not in agreement with the mean positions determined from the astronomical observations. It was primarily for this reason that the observations were carefully collated by Lieutenant J. M. Child, R.N., and forwarded to the Admiralty. The observations were in due course sent to H.M. Nautical Almanac Office, where it was decided to subject them to a detailed statistical analysis. They are not suitable for inclusion in the (deliberately) heterogeneous observations being collected for the working party of the Institute on the accuracy of astronomical observations at sea; but they provide the ideal material for a pilot investigation into methods of analysis.

In the early days of air navigation, dead reckoning procedures were inevitably closely allied to those practised at sea, but the rapid development of aviation has considerably reduced these early similarities. To talk generally of D.R. practices is therefore no longer feasible. It is the purpose of this article to outline some of the air procedures and instruments in use, and to give an indication of the reason that lay behind their adoption.

When the Society for Nautical Research was founded in 1910, one of its objects was to work for the foundation of a National Maritime Museum. To many this must have seemed an unattainable star on which to focus their hopes, especially when a few years later the First World War broke out. However, fortune changed, and in 1928 the great Macpherson Collection of maritime prints and drawings came on the market. A fund was started to purchase it for the nation, but Sir James Caird, a wealthy shipowner, stepped in and bought the entire collection. Matters now really began to move. The Admiralty was anxious for more space in the Royal Naval College at Greenwich and this could only be obtained by removing the Royal Naval Museum, which had been transferred from Somerset House, and the Greenwich Hospital collection of paintings, which had been started in the Painted Hall in 1824. A new home was needed for these and for the Macpherson Collection, and then in 1933 the Greenwich Hospital School was moved to Holbrook, and the great range of buildings just across the road from the Royal Naval College became available. In the next year the National Maritime Museum was established by Act of Parliament and the conversion of the buildings was begun; but already fresh acquisitions had begun to come in. Sir James Caird bought such treasures as came on the market and, capably advised by the distinguished naval historian, Sir Geoffrey Callender, who was to become the first director of the museum, laid the foundations of a collection which has become the envy and admiration of maritime nations.

One of the earliest publications about ocean currents was Dampier's Discourse of Winds, Breezes, Storm Tides and Currents published in about 1700. Dampier wrote his book in 1688 and he says:

By currents I mean a motion of the sea which is different from the tides in several respects—both as to its duration and also as to its course; currents run a day, a week, nay sometimes more one way, then it may be, run another way. In some places they run six months one way and six months another. In some places they run constantly one way and never shift at all.

After some remarkably detailed discussion of currents in the West Indies and off the coast of Africa and in the south seas he says, of the Indian Ocean currents, ‘north of the line the current stays with the monsoon but does not shift altogether so soon, sometimes not for three weeks or more and then never shifts again till the monsoon is settled in the contrary way’. Of the Gulf Stream he says, ‘near the shores on each side of this Gulf there are tides, especially on the Florida shore, and ships may pass which way they please, if they are acquainted’. In conclusion he says, ‘I humbly offer this not as a complete and perfect account but as a rude and imperfect beginning or specimen of what may be done by abler hands hereafter’.

It is widely known that whilst radar is almost unaffected by the densest fogs, some reduction of its performance must be expected in rain, and sometimes considerable reductions under conditions of very rough sea. Little practical data have been available to the mariner on the extent of reduction which may be expected in rough sea conditions and this short paper will attempt to provide some practical information on the subject.

When using radar in thick weather as an anti-collision warning device it is necessary, when planning any manœuvre, to consider the effect of the proposed alteration of own vessel's course and/or speed on the PPI presentation of the target vessel's radar, should she be using it. An alteration of course or speed of own vessel will alter the direction or speed of the apparent motion of the spot on the target vessel's PPI. As the apparent motion on relative plots kept by the two vessels are reciprocal images of each other it is a simple matter to determine, in any particular case, the effect on the target's plot of own vessel's manœuvre by considering the effect on the apparent motion on own vessel's plot.

The following is a summary of a lecture given to the Institute, in the Science Museum's lecture theatre, on 5 May 1954. Dr. G. E. R. Deacon, F.R.S., Director of the National Institute of Oceanography, was in the chair. The lecture was illustrated by slides and a film.

Alexander the Great was probably the first deep-sea diver. He is supposed to have had a glass boat made and to have spent some ninety days under the water observing strange and rare animals which, it may be conjectured, were no more than mythological. Since that time a number of attempts at producing diving spheres were made, but apparently without success until in 1832 a Spaniard made one of wood, which he went down in, and, unfortunately, never came up. In 1892 a steel sphere was made by an Italian, Balzamello, who reached a depth of 165 metres. The next developments were those of the Americans Beebe and Barton, much later, in 1930–34. They dived to 908 metres in a sphere attached to its parent ship by cable. Later on Barton by himself achieved 1380 metres.

Francisco Radler de Aquino, one of the first of the Institute's few Honorary Members, died on 8 October 1953 in his seventy-fifth year, but his death was not officially notified to the Institute for some months. He had been in failing health for some years, but had made sufficient recovery from a serious illness to prepare, and practically see through the press, still another volume of tables. He had retired from the Brazilian Navy in 1935 at the age of 57 with the rank of Captain; and it was not until sixteen years later, on 24 March 1951, that he was given the belated promotion to Vice-Admiral: the reasons for the delay were obscure but apparently political. By his death the science of navigation will lose one of its most stalwart champions and one of its most prolific writers. The field of tables for astronomical navigation will hardly seem the same without his colourful personality and his constant additions to his many publications. Many, including those who did not always agree with his views, will miss him as a friend, even though that friendship had largely been carried on by correspondence.

In the discussion following the papers read on ‘Methods of Air and Surface Navigation’ at the Institute meeting on 15 January 1954 (see pages 159–164 of the Journal, Vol. VII, No. 2, April 1954), the question was again ventilated of including PPI pictures in the Admiralty Pilots or Sailing Directions.

The writer has drawn the accuracy contour maps of a ship's position fixed by cross bearing, horizontal sextant angle method and Loran aid. The accuracy of the fixes has been evaluated in terms of the probability density.

Captain G. C. Forrest's letter (this Journal, Vol. VII, p. 203) raises some interesting points well worth discussion:

‘(1) That radar-using ships, taking broad evasive action, shall alter course to starboard only, and not at all once they are within five miles of the other vessel, though they may reduce speed or stop.’

The following discussion, here printed in summary, took place on Mr. E. S. Calvert's paper ‘Visual Judgments in Motion’, which was presented at an Ordinary Meeting of the Institute on 21 May. The chairman was Air Chief Marshal the Hon. Sir Ralph Cochrane, G.B.E., K.C.B., A.F.C. The paper was printed in the last number of the Journal (July).

The Chairman: Am I right in thinking that I.C.A.O. have accepted the Crossbar system of lighting? Is it the normal pattern in international airports?

A total eclipse of the Sun provides an opportunity, rare though it may be, of obtaining an instantaneous fix from the Sun alone. Eclipses vary greatly in character, in position on the Earth, in the width of the path of totality, in the duration, and also in the direction of the path. However, the shadow of the Moon cast by the Sun is always a right circular cone which, in the case of a total eclipse, intersects the Earth's surface at some point before its vertex. Owing to the motion of the Moon in its orbit round the Earth the shadow moves at a speed of about 2000 m.p.h. from west to east (it varies considerably according to the distance of the Moon from the Earth).