The wind pattern in the North Atlantic (Fig. 1) is more or less clockwise, and therefore the easiest way to cross the Atlantic from east to west is by the southern route, and from west to east along the northern route. In between, in the middle of this rotary system, are the horse latitudes where winds tend to be light and variable. Superimposed on this wind system, of course, is a series of depressions which commonly move from west to east across the North Atlantic, each depression having its own system of winds rotating anti-clockwise: on the south side of the depression winds tend to be westerly whilst on the north side they tend to be easterly.

Tactics were clearly going to be vitally important in this race, and the first tactical decision was obviously which route to take across the Atlantic. Using a dry-sail method, I worked out the speed at which the boat should sail over about twelve routes or combinations of routes. The method used was to compute from the appropriate monthly Pilot Chart of the North Atlantic (issued by the U.S. Hydrographic Office) the time it would take to cross each area measuring 5° of longitude by 5° of latitude, using the average winds determined over a long period of years. For example, in the first area (Fig. 1), from Plymouth to 5° west, the average wind blows from the west for 18 per cent of the time in June, which should give a rate of advance towards the objective of something like 2½ knots for that period. For the north-westerly and south-westerly winds which, according to the chart have blown for thirty two per cent of the time, at an average of force four, I estimated that I should travel at 4 knots towards the objective: so, similarly with different speeds for beam and following winds, I calculated that I should be able to cross this area in 62 hours. In practice it took 103 hours—more than 4 days instead of 2½—due to head-winds of from force 6 to gale force. However, this wrong estimate did not spoil the value of comparing the routes.

As part of an investigation into the difference of absolute sea-level across the English Channel, a detailed series of measurements of currents at all depths was recently made in the Strait of Dover. The main object of the measurements was to relate the residual non-tidal flow of water to the voltage on a cross-channel cable generated by electromagnetic effects. Over 6000 readings of current strength and direction were made during ideally calm conditions. This paper describes the results of analysis of these measurements, which covers vertical current profiles and tidal components, besides the non-tidal flow. Distinction is made between mean current measured at a fixed depth or at the surface, and the mean volume flux of water which involves tidal variation of depth. A method of tidal analysis based on Fourier sums, which is convenient for use with an electronic computer, is outlined in the Appendix.

This paper describes a number of occasions on which German ships have successfully avoided tropical revolving storms by using information which is at the disposal of the mariner today. Similar accounts could obviously be given of storm-avoidance by the vessels of other countries, but it is thought that this compilation, by a member of the German Weather Service, will interest many seamen. The paper was presented at a meeting of the Ausschuss für Funkortung held at Kiel on 10, 11, 12 September 1960, and is published with the kind permission of that body.

When two ships encounter one another at sea, there is a possibility that they will collide. Whether there is actual danger or not depends on the physical facts of their respective positions and motions. If danger does exist, the motions must be changed. The purposes of Dr. Morrel's paper are (1) to inquire what facts must be known, both to distinguish the cases of actual danger and to choose effective remedial action; (2) to determine when and how well these facts must be known; and (3) to consider how these facts may be obtained and how they may be best utilized.

The paper attempts to construct an integrated treatment of the whole problem, in terms of the fundamentals that define its nature and shape its solution. The problem is large and complex. Consequently, a compact treatment of it must perforce omit most of the details; both of the evidence and analysis by which the principles are established and of the technology by which they may be exploited.

Much of the treatment uses mathematics; but emphasis is placed on the implications rather than on procedures.

The paper was presented at the meeting of the Ausschuss für Funkortung held at Kiel on 10, 11, 12 September 1960 and is printed with that body's kind permission.

1. Journal de bord de Juan de la Cosa, second de Christophe Colomb. Presenté et commenté par Ignacio Olagué. Paris, 1957, 870 frs.

2. The Journal of Christopher Columbus. Translated by Cecil Jane, revised and annotated by L. A. Vigneras with an appendix by R. A. Skelton. Anthony Blond and The Orion Press, London, 1960, 45s.

Writing an Introduction to the Four Voyages of Columbus over thirty years ago, the late Cecil Jane remarked: ‘It might with justice be added that no event of such moment can ever occur again, unless, perhaps the tracts of space be bridged and communication established between the Earth and her sister planets.’ The fact that we are on the very eve of placing a man in the Moon should enable us to appreciate more justly the various ways in which, during the late fifteenth century, different people reacted to the daring proposal of Columbus to sail west to Asia.

An attachment giving a number of accurate straight or curved climb or descent flight paths has been developed for use with the Australian-designed airborne distance measuring equipment (DME). The electrical output from a special altimeter is converted into a time delay which increases with altitude. In the DME distance is measured, fundamentally, in terms of a similar time delay. The h/d flight path is defined by keeping these two delays equal as the aircraft climbs or descends. The ILS glide slope meter is used as the pilot's path indicator. Nominal slopes from 1° to 6° may be selected. In terms of height, deviations from the path of ± 250 ft. produce full-scale deflections on the meter, while the maximum error is ± 1000 ft.

The use of leading marks in pilotage is a procedure familiar to all seamen, and wherever leads are sufficiently easy to recognize on the screen the technique can be extended to use with radar, due note of the lowered degree of precision being taken. In this account of a passage through the exit to Singapore Strait, Captain Robb, a shipmaster of the Blue Funnel Line, and author of several works on radar use at sea, describes a less well known method in which off-set marks are used for conning the ship by radar. A similar technique was suggested in the Journal (9, 445) by Mackay.

A star globe is described which can be immediately set up for evening or morning twilight by adjusting the latitude and date only; no reference to the Almanac is involved. The azimuth of the below-horizon Sun is also directly evident. The paper discusses the theory involved, and the accuracy attainable both with and without certain simple corrections.

A joint symposium of the Institute and the British Interplanetary Society was held at the Royal Geographical Society's house on Friday, 18 November 1960.

At the morning session the Chair was taken by Wing Commander E. W. Anderson, o.b.e., d.f.c., a.f.c., President of the Institute, who introduced the speakers. In the afternoon, Dr. W. R. Maxwell, President of the British Interplanetary Society, took the Chair for the papers by Cashmore and Stewart, and Air Marshal Sir Edward Chilton, k.b.e., c.b., presided over the main discussion, which was opened by Dr. J. G. Porter.

As every schoolboy learns, a point has position but no size, and a line has length but no breadth. Nevertheless, to a navigator concerned with fixing his ship, points and lines are represented on his chart as fine pencil marks.

The manner of representing the results of observations as pencil ‘points’ or ‘lines’, has undoubtedly led to the belief that a ship's position must be represented as lying at a point on a position line which is drawn on a chart. Nothing short of perfection in position lines is ever expected by most practical navigators, and two position lines crossing at a point are usually regarded by seamen as yielding a perfect position: and if three position lines meet at a point! … there is seldom even the slightest doubt in the mariner's mind about the reliability of such a fix. On the other hand, three position lines which do not meet at a point are usually regarded as being something not quite respectable.

The problem of errors in radar plotting were considered by Capt. H. Topley (11, 167) and Capt. F. J. Wylie (12, 198), and it was shown that the error in the estimated distance of the C.P.A. depends upon mean range and range change in plotting interval. I want to introduce the term rate of error in the estimated distance of C.P.A., in the same way that Topley shows the percentage error in the estimated speed.