Although an X-craft is a complete submarine in miniature, it does not fire torpedoes but carries two large mines which are dropped under the enemy ship at anchor in its harbour and time-fused to explode when the X-craft has retired to a safe distance. Each mine—or side-charge, as they are called—carries a heavy weight of explosive, but is fitted with internal buoyancy tanks so that its weight on the boat in water is negligible. Each side-charge is faired nicely to the hull to avoid catching nets or wires and well streamlined to keep its effect on the boat's performance to a minimum. In this article I will illustrate some of the navigational problems which arise in operating X-craft by giving an account of the attack we made on the Tirpitz in 1943

This paper sets out to describe some of the ways in which merchant seamen may make useful sketch surveys of anchorages, coastlines or even whole islands, so as to improve the official charts, plans and sailing directions in areas which lack complete surveys by naval surveyors. These areas in fact include hundreds of miles of coastline, and hundreds of square miles of water where the depths are dangerously uncertain. The paper also describes some unorthodox uses of the official charts and, finally, attempts to show the usefulness of these improvements. All the work described has been done in the south-west Pacific, among the islands of Melanesia, where good surveys are few, and the gaps are filled in with scraps of early surveys.

In the course of collecting data for a general history of scientific instruments, Dr. Price came across the manuscript that forms the subject of this volume in the Library of Peterhouse, Cambridge. It attracted his attention because of its subject matter, because it was written in Middle English, and because the date 1392 frequently occurred. As Chaucer's Treatise on the Astrolabe was written in 1391 and is apparently incomplete, it seemed at first sight possible that the Peterhouse manuscript might be a missing part of Chaucer's Treatise, which at that time was the only instrument tract written in Middle English known to Dr. Price.

In October 1954, Aries IV, a Canberra aircraft from the Royal Air Force Flying College, made the first flight by a British jet over the North Geographical Pole. This paper describes the navigation aspects of that flight, together with a later series of training flights for which it was a preparation.

For several years it has been the practice for navigator students at the Royal Air Force Flying College to carry out high-latitude flights as part of the normal syllabus of training. Hitherto only piston-engined aircraft have been used, but in 1954 it was decided to extend the scope of activities to include Canberras, the first flights to take place in December of that year from an airfield in northern Norway. A preliminary survey was necessary to confirm the practicability of the proposed navigation technique under actual conditions, and it was agreed that this should take the form of a flight towards the North Geographical Pole. A further object of the survey was the selection of a suitable operating base; the choice lay between Bardufoss and Bödo.

The use of an airfield is controlled to a certain extent by the wind, and if the cross component of the wind on the runway exceeds a certain strength, it becomes hazardous for an aircraft to land or take off. The effect of a cross-wind component on aircraft in flight is to cause drift, whereby the path of the aircraft over the ground is inclined at an angle to the direction in which the aircraft is steered. A pilot about to land in a cross-wind must execute a certain manoeuvre to counteract the drift, otherwise on touching down the aircraft will tend to move sideways across the aerodrome, thus putting a strain on its undercarriage and perhaps tipping over on to one wing.

Most people know something about space ships nowadays, and probably think that navigation in space is quite a simple matter; at any rate, it is a subject that is glossed over very briefly in most books on the subject. In my view, space navigation is not a simple matter, and it has certainly not received the attention it deserves. Navigation on the Earth is easy, because of the one important fact that you are on the surface of the Earth. A couple of sights, measuring the angles from two stars down to the horizon, together with the azimuths of the stars and the distance from the centre of the Earth, will give an exact statement of position. But out in space there is no Earth, no horizon—in fact nothing whatever to use as a basis of measurement. Clearly then, two angles are not enough; a third one is needed, to give a sort of tripod of sights—two of the legs being anchored to two planets (or the Sun and a planet) because their positions in space at any time are known, and the distance between them can be used as a base-line. The solution of all the triangles involved is indeed a difficult problem, but there is also the impossibility of making three simultaneous observations. It might be thought that one could do as at sea and take one sight followed later by others, making allowance for the motion of the ship in the intervals. However, this involves the idea of dead reckoning, which, although a useful concept at sea, is quite impossible to apply in space, as the following example shows.

The discussion following Captain C. V. Sølver's claim to have discovered an early Norse bearing-dial incidentally raised the question of what was the ‘dyoll’ referred to in English ship inventories of the fifteenth century. There are various practical reasons for doubting the theory that it was a compass-dial, that is to say a sun-dial with an inset compass, which for a particular latitude would, when correctly orientated, indicate the time of day. However, the idea that the ‘dyoll’ indicated time rather than direction seems to fit the evidence, and G. P. B. Naish's note on fifteenth- to seventeenth-century ship inventories leaves little doubt that it was an instrument for measuring equal intervals of time, and probably a sand-glass. This conclusion, which to some extent casts the early history of the compass card once more into the melting-pot, prompts a number of questions. Some are stated here and are answered either wholly or in part. Others remain to be answered.

Recently two ships of the Holland-Amerika Line carried out speed trials, using the Decca system. With the permission of this company, which has shown great interest in this new method, the results of the trials are given in this paper. For comparison, some figures for trials on a measured mile are also given.

The note in the Forum ‘The Accuracy of Astronomical Observations at Sea’ by G. A. Harding (this Journal, Vol. VII, p. 195) and the paper ‘The Barcoo Observations’ by J. B. Parker and D. H. Sadler (this Journal, Vol. VII, p. 317) were interesting, but although some practical navigators have dabbled with the theory of errors one is apt to feel a little bit blinded by the science of the mathematicians on the subject of ‘errors’, when such things as ‘constant bias’, ‘quasi systematic error’, ‘internal standard deviations’, and a ‘ square root law’ (p. 320, Table I, Col. 7) are bandied about. One hopes one knows what they mean, but there is a lurking doubt, though one might not admit it, and they do not quite seem to click with the sort of phrases taught to navigators.

For the satisfactory understanding of the mechanical effects which occur in an aircraft landing in a gusty wind it is necessary to know something of the time-scale of the wind fluctuations during the moments when the aircraft is touching down. Such information can only be given on a statistical basis but it so happens that there is a body of data on the subject which may not be generally appreciated.

I think the Institute is doing a grand job in this matter of getting to the bottom of what actually happens at sea. I give a personal ‘shabash’ to D. H. Sadler & Co. for the new Abridged Nautical Almanac, and to S. M. Burton for the first-ever really practical manual and tables, but I am now completely ‘sold’ on H.D. 486 [Tables of Computed Altitude and Azimuth] and have very little to look forward to unless it be my dream of ‘a small hopper, into which one throws two or more altitudes, turns a handle, and tears off a neatly printed position’. I can see no loss of caste to seamen in this. All I ever did know about a haversine, for example, was that it contained a conglomeration of figures which when conjoined with others, cosines and suchlike, led by tortuous and unseamanlike stages to a position line on a chart. I never felt the slightest bump when crossing over to H.D. 486, where all those abominable spherical trigonometrical triangles have already been worked out by experts who, I understand, really like 'em. So roll out that hopper.

It is a notable compliment to the captains and masters (particularly to the masters) who served Elizabeth I that she lost no important ship of her Royal Navy by stress of weather or by stranding throughout her long reign. She lost two ships to the enemy for both the Jesus of Lubeck and the Revenge surrendered to superior Spanish forces after hard fights. The Revenge was a moderate-sized ship or galleon of 450–500 tons, described by Monson as being ‘low and snug in the water, like a galliasse’. She was built at Deptford in 1575–7 and carried a ship's company of 250 men and an assorted armament of 38 guns, large and small. Although of middle size, she was Drake's flagship in the Armada campaign and again in the voyage to Lisbon in 1589. She was Frobisher's flagship in 1590 and Grenville's in 1591, when she was captured in epic circumstances and soon after capture overwhelmed in a hurricane with her prize crew. In August 1579, when she became the flagship of Sir John Perrot in a voyage to Ireland, she was a new ship. Her master was John Gray, who was still her master under Drake in 1588. The Revenge was considered an unlucky ship. Both Sir Richard Hawkins and Monson list the tale of her misfortunes and Hawkins writes of her : ‘The Revenge, which was ever the unfortunatist ship the late queen's majesty had during her reign; for coming out of Ireland, with Sir John Perrot, she was like to be cast away upon the Kentish coast’. He blames her name for this ill-luck, for revenge should rightly be taken by God alone and not by man.

The word Navigation still retains the broad meaning it had in 1570, when John Dee wrote: ‘The Arte of Navigation, demonstrateth how, by the shortest good way, by the aptest Direction, & in the shortest time, a sufficient Ship, between any two places (in passage Navigable,) assigned: may be conducted: and in all stormes, & naturall disturbances chauncyng, how, to use the best possible meanes, whereby to recover the place first assigned’. But for the purposes of the Science Museum it is convenient to restrict the scope of the so-called Navigation Collection to objects illustrating the development of methods of determining a vessel's position and course. Exhibits illustrating the other aspects of navigation are placed in the Marine Engineering and Aeronautical collections.

This paper was presented by Captain Wylie, in Boston in October 1954, at a meeting of the (U.S.) Radio Technical Commission for Marine Services, with whose kind permission it is here reproduced. The paper was one of a series which discussed whether further additions to radar could help reduce the number of collisions at sea. Captain Wylie made clear that the views he expressed were not necessarily those of the British shipping industry.

The preliminary to the Steering and Sailing Rules state: ‘Risk of collision can, when circumstances permit, be ascertained by carefully watching the compass bearing of an approaching vessel. If the bearing does not appreciably change, such risk shall be deemed to exist.’ What is to be taken as ‘appreciable’ when considering a change of bearing is not defined, but the watchkeeper at sea in clear weather has his accumulated experience to call upon and no difficulty is normally encountered in deciding on the degree of risk, except in the case of using radar in thick weather, when the watchkeeper has not the benefit of long experience. The purpose of this note is to consider the conditions under which the nearest approach can be estimated and to determine the accuracy of the estimate.

There is a fast growing realization that the Steering Rules in the Regulations for Preventing Collisions at Sea should be attuned to the use of radar. The principle underlying the suggested rules which follow is to stick to the idea of Rule 18—that in case of risk of collision both vessels should take avoiding action. In order to make these rules practicable, a universal system has been thought out. Thus, the rules are meant to apply to vessels in sight of one another, as well as to vessels in radar-contact, or to a vessel in radar-contact with another vessel which is unaware of her presence. Secondly, there will be one and the same rule for power-driven vessels and sailing vessels.

A series of overlapping photographs taken from a aircraft flying straight and level can be used to indicate the strength and direction of the wind, by noting the displacement on successive prints of the centre of the photograph, which is assumed to represent accurately the position of the aircraft at the time the photograph was taken. The method has the advantage that an almost continuous record of the wind can be obtained; it can be used over virtually any ground surface (though not over the sea) and the results of a long flight can be fairly easily and rapidly assessed. No detailed identification of the ground on a map need be made.