I am making my second Presidential Address the opportunity to do little more than muse aloud on a theme which is fashionable rather than original. It will be entirely personal and in no way representative of Admiralty views. I can describe the theme as the way in which man is getting along, in our particular field of navigation, with his inventions of mechanical devices, or as Shakespeare collectively and descriptively calls them—his ‘engines’. I could alternatively and not unreasonably describe it as the way in which man is becoming increasingly dependent on his mechanical aids. Yet, that would convey an impression of his going into an unduly early decline or of his doing something wrong. Obviously, he gains in being able to achieve things which he could not do unaided, but obviously, also, he must avoid rendering himself helpless if there is a chance of his inventions failing him at a critical moment.

It was a trial and a torment to sailors when it was brought home to them that the magnetic needle did not point truly to the north, but ‘northeasted and northwested’ as they described it. ‘El nordeaster de las agujas pone alos mareantes en muches dudas’, wrote one of them, and many flatly refused to believe it, putting discrepancies down to the use of a faulty lodestone or to bad workmanship on the part of the compass-maker. In the far-off days when the use of ‘needle and stone’ to recover lost bearings was first discovered, they believed that by some magic or divine sympathy the needle turned and pointed to their star, which they called the Shipman's Star, or Stella Maris, the only one that never moved. But Peter Peregrinus, writing the first scientific treatise on magnetism in 1269, remarked that they were wrong. The needle pointed to the celestial pole, round which the Pole Star circled like any other. And three centuries later Peter in his turn was faulted by the Elizabethan mathematician John Dee, who scribbled a note in the margin of the medieval writer's book to the effect that it was neither the star nor the pole which was the centre of attraction, but a spot on the Earth—the magnetic pole.

An investigation has been made into the frequency distribution of errors in equivalent tail-winds on the great-circle air-route Shannon to Gander, as forecast at London Airport. In the course of the analysis the frequency-distribution of ‘actual’ equivalent head-winds as measured from the synoptic upper-air charts was also examined, and compared with seasonal means already published. The monthly extremes are tabulated and quarterly mean and standard errors are given, with frequency curves for the summer and winter half-years.

In this paper values for the accuracy with which the meteorological forecaster can assess a route wind at 40,000 feet between London and Rome from his chart are suggested, and the accuracy with which he can forecast what the route wind will be is then calculated. These figures are then compared with an estimate of the accuracy of route winds derived from the navigation of aircraft over the route. Estimates of the errors that are likely to occur in wind forecasts for various air routes in operation or in contemplation are then made and a method of using wind forecasts is suggested.

Ever since the introduction of the Air Almanac and the Astronomical Navigation Tables, requests have been received for information as to the errors that can arise in their use. Estimates of error, for particular combinations, were made on several occasions and, in 1947, the calculation was systematized; but the methods and results were not published. It is now probable that the Sight Reduction Tables for Air Navigation, A.P. 3270 (H.O. 249 in U.S.A.), and possibly the Air Almanac, will increasingly be used for surface navigation and it therefore seems desirable to put on record a precise statement of the errors that can arise through their use. The earlier work has accordingly been modified for the changes in the publications.

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.

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.

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.

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.