A New measure of time, Ephemeris Time, has recently been introduced by astronomers. The purpose of this short article is to explain briefly why this has been necessary and how it will affect navigation.

In order to obtain some experience of problems that were likely to be encountered in the operation of the Comet III across the North Atlantic, B.O.A.C. decided early in 1954 to conduct a daily ‘paper’ operation between London and New York. The aircraft was planned to depart from London at 1000 G.M.T. each day. It was felt that the production of operational statistics on the basis of a daily operation in this way would enable the Corporation to compile useful information on such vital subjects as elapsed times, payload capacity, fuel uplift requirements, the frequency with which particular routeings were likely to be used and the adequacy of existing meteorological telecommunications and air traffic control services. In order to obtain the basic meteorological data for planning flights it was necessary to enlist the cooperation of the London Airport Meteorological Forecasting Unit and their most helpful cooperation played an important part in the results achieved.

It seems unfortunate that with the great advances made in modem navigation, the elementary and basic problems have been left unstandardized, incomplete and to a certain extent misleading, causing needless confusion to the student.

On 23 July 1954, the new Canadian Icebreaking Patrol Vessel H.M.C.S. Labrador (6000 tons) left Halifax, Nova Scotia, on her maiden voyage in support of the annual ship supply mission to the Canadian Arctic bases. In addition she carried out much hydrographic surveying and other scientific work, and subsequently withdrew to the westward, arriving at Esquimalt, British Columbia, on 27 September, thus becoming the first warship to complete the North-west Passage.

The past few years have seen a great increase in the amount of traffic at airports throughout the world. Today a rate of thirty aircraft movements per hour is by no means unknown and sixty movements per hour can realistically be forecast for the near future.

I was unable to attend the lecture by Mr. C. S. Durst on ‘The Accuracy of Dead Reckoning in the Air’, and I was, therefore, very interested to read the paper in the April Journal. There are many implications, and Mr. J. B. Parker has endeavoured to suggest some in his article.

Although only a small percentage of the world's total tonnage is involved, the number of collisions which take place at sea each year is large. There must also be a fairly large number of ‘near misses’, and, daily, officers have to consider the implications of situations which could give rise to collision. It is by no means certain that all seafarers put the same interpretation on the Collision Regulations or on such phrases as ‘the ordinary practice of seamen’, ‘ample time’ &c. Indeed, with some 1600 to 1850 collisions each year, it is almost certain that they do not.

Dr. Atkinson puts up an interesting hypothesis which I hope will not appeal to many sailors, because I do not think it offers what the navigator needs and I believe that it could be misleading. As far as concerns other plots discussed in the Journal or The Use of Radar at Sea, the criticism that they do not use all the information available is, I think, quite invalid.

Beyond is a 43-foot auxiliary Bermudian cutter, specially designed and built for a voyage round the world. Between August 1952 and September 1954 she sailed some 30,000 miles, the track being shown on the chart (Fig. 1). From Lisbon to Auckland we were four aboard, but from Auckland back to England there were only my wife and myself. The following notes record the various methods of navigation.

The full value of A.P. 3270 (Sight Reduction Tables for Air Navigation, Vol. I, Selected Stars, H.M. Stationery Office) does not yet seem to have been fully appreciated by surface navigators. As well as increasing the speed with which sights can be reduced, the tables offer all the advantages of a star globe or planisphere in planning a series of sights. The navigator can thus concentrate on the most suitable stars for cut, magnitude and azimuth. Since observations can be planned for a time at dusk when the horizon is still firm and the star just visible through the telescope (or, at dawn, when the star is still visible and the horizon firm), a more accurate sextant altitude can be obtained.

I cannot subscribe to Dr. Freiesleben's thesis that until the French Revolution induced a change of mind there was a big gap between men of science and seamen. It may be, as he states, that ‘in the eighteenth century there was still a remarkable gap between scientific doctrine and practice’ and it would be interesting to know the causes if this were so, but in the sixteenth and early seventeenth centuries there was, particularly in England, a quite remarkable and organized liaison between scientists and seamen with the specific purpose of improving the art of navigation. The object, as Thomas Digges expressed it in 1579, was ‘to reduce Imaginative Contemplations to Practical Conclusions’; in other words, it was to make scientific discoveries and inventions to improve the accuracy of navigation. A few examples must suffice in the space available to support this statement.

A number of members have been invited to contribute to a general discussion on the value of meteorology to navigation. It is hoped to follow Mr. Williams' contribution with others dealing with different aspects of the subject.

Years ago there was weather in which birds and airmen alike walked. Now, although operations through particular airports affected by below-minima weather may be interrupted, airline services are rarely cancelled because of weather en-route. As aircraft tend to fly faster and higher, and navigational aids slowly improve, the weather information required by the short-range operator tends to be conditioned by the question: Can my aircraft operate through airport X at time T? The long-range operator is still interested in two other questions: What route will give the most favourable component, and What is that component? Having the meteorologist's answer to these and other, less vital, questions, the operator plans his flight on the assumption that the forecast is quite correct and equips and fuels his aircraft on the assumption that it is wholly false. The operator has learned to compensate for the errors of forecasting; possibly all the airline accidents in recent years in which unexpected weather deterioration played a major part could have been avoided with sound airmanship. The most realistic way, therefore, to consider the value of forecasting to airline operation is to attempt to evaluate the cost to operators of the measures they take to protect life and equipment against forecast error and speculate on what would happen if no forecasting were attempted.

Historians of the mariner's compass (particularly those of the last century) have introduced into the literature of the subject a number of statements which can be shown to be incorrect, or at the least to be extremely doubtful. Unfortunately it is just these ‘facts’ which have been seized upon by later historians and appear in one authoritative book after another. I have myself fallen into one stock trap or another in the past.

I think that the impression which would be left by the Institute Working Party's Report (Journal, Vol. VII, p. 219) in the mind of any of the learned gentlemen of the Admiralty courts would be that a ship which did not keep a radar plot should be considered guilty of ‘neglect of any precaution’ under Article 29 of the Collision. Regulations, and this impression could lead to a miscarriage of justice.