The following discussion on marine pilotage took place at an Institute meeting held at the Royal Geographical Society on 19 February 1954, with Wing Commander E. W. Anderson in the chair. Commander Akerman, who has had considerable experience as a Trinity House pilot, first of all outlines the general requirements of navigation in restricted waters, and Mr. Hansford then proposes what he conceives to be the best solution at the moment to the problem of pilotage in poor visibility. Both contributions are here presented in summary.

In describing progress in the development of a functional equipment, it would be quite normal to begin by defining the technical targets at which the engineers are aiming and the operational uses to which it will be put. In the case of marine radar, however, it is not possible to be precise in either of these matters. It might be said that the ultimate target is to make port, coastal and open sea work as safe and straightforward in poor visibility as in good; or, put in another way, to replace direct human vision in poor visibility and to improve upon it at any time when the distance of targets is to be measured with accuracy.

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 problem of navigating a vessel under conditions of bad visibility in open sea and in coastal waters has in recent times been largely solved by the advent of modern aids. The problem in pilotage waters, however, still remains severe and the handling of a sizeable ship in estuaries and harbours in bad visibility is today the exception rather than the rule.

The lack of progress in this field is due mainly to two causes. The first of these causes is the lack of a clear understanding of the pilotage requirements; the discussion at this meeting may help to shed some light on this problem. The second is referred to later. Commander Akerman has stated some of the pilot's requirements and the object of the present paper is to illustrate and further clarify the problem by examining some of the possible systems available to aid its solution. The paper will concentrate on radio systems since these seem the ones most likely to aid in solving the bad-visibility problem.

In the July number of the Journal Captain C. V. Sølver described the discovery, by the Danish archaeologist Dr. C. L. Vebæk, in Greenland in the summer of 1951, of what was believed to have been part of an early bearing-dial. The object, which was dated by the archaeologists at about the year 1200, was one-half of an oak disk the outer rim of which was carved in such a way as to lead Captain Sølver to the conclusion that the complete disk was divided into thirty-two points or directions. Captain Sølver's paper was illustrated by a photograph of the fragment discovered and of his reconstruction of a similar bearing-dial.

Professor Taylor comments below on Captain Sølver's paper, and on the more general question of a Norse bearing-dial which it raised. Comment on the problem invited from a number of members and others is also given.

On 13 flights at different heights and outside air temperatures a total of 127 low-altitude sights were taken of the Sun, Moon and planets. The sights were taken with a Kollsman periscopic sextant which uses an illuminated graticule as a datum. Hughes' Tables were used for the calculations and the corrections for refraction taken from the table published in Navigation.

Anchor work is generally considered to be a question of seamanship rather than navigation; Commander Sharpey-Schafer's paper, which deals with a number of subjects only indirectly allied to navigation, is, however, presented here because what he has written will be of interest to so many navigators.

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.

The term ‘Priming and Lagging’ has been defined in two different ways.

The Admiralty Manual of Navigation (1922) defines it as occurring when the resultant of the solar and lunar tides arrives before or after the lunar tide would arrive. This is here called definition A. The Admiralty Manual of Tides (1941) defines it as occurring when the interval between successive diurnal high waters is less or more than the average 24h 50m. This is here called definition B.

It may be interesting to report some measurements of refraction which Professor A. N. Black and I made this winter. These were made on the setting Sun, and as the altitude of the observing station was 480.0 ft. it was possible to carry the observations down to the horizontal and, in fact, under clear conditions, to −20′.

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.

In his review of Sight Reduction Tables for Air Navigation (A.P. 3270) on page 98, Mr. J. B. Parker suggests that navigators might tolerate the disadvantage of tables with large intervals in the arguments. Mr. D. H. Sadler, Superintendent of H.M. Nautical Almanac Office, comments on this suggestion as follows:

Mr. Parker's suggestion is most intriguing. A substantial reduction in bulk would be possible, as the following table of approximate figures shows.

Mr. J. B. Parker, in his review of Sight Reduction Tables for Air Navigation, published on pages 98–103 of Vol. VII of this Journal, states that the time required by him to resolve a three-star fix by means of A.P. 3270 is 10 minutes (p. 100). He comments on the ‘errors due to the plotted fix being a hundred or more miles behind the aircraft's position’ (p. 101). Later he says: ‘An accuracy of sight reduction of anything better than certainly 5 minutes of arc, and more logically 10 minutes of arc, will therefore be wasted on a navigator flying with present-day instruments in a fast modern aircraft in high latitudes’ (p. 102).