The servicing of ships off Cape Town by helicopter with stores and spares is now established practice. In addition, test exercises are in progress with the Rotterdam Port Authorities to embark pilots by helicopter, and preliminary enquiries are under way for helicopter servicing in the Arabian Gulf.

Since the Institute is setting up a working party to consider the revision of the Collision Regulations, this may be a suitable time to raise the question of whether or not a vessel being serviced by helicopter or embarking a pilot by helicopter should be required to exhibit the day-time shapes prescribed in the Collision Regulations under Rule 4(c).

From exchange of correspondence in recent weeks with various interested parties, it is noticeable that there are differences of opinion concerning the necessity for helicopter serviced vessels to exhibit specific shapes, notably those required under Rule 4(c), and due to the non-existence of published official ruling, the following notes may be of general interest.

Mr. Bell and Professor Stratton have in the October Journal shed interesting light on the nature of inertial navigation as applied to navigation around a planet. It is a pity that Mr. Bell has repeated that in such inertial systems vehicle position and velocity are deduced from measurement of acceleration. This idea is certainly misleading so far as understanding error propagation in these systems is concerned, if not actually wrong.

The aim of this paper, which was presented to the last meeting of Icotas (London, 14 January), is to show how the manœuvres proposed by Calvert (Journal13, 127) and by Hollingdale (Journal14, 243) could be incorporated in the International Regulations for Preventing Collisions at Sea. Calvert's objective was, as Hollingdale points out, to establish a set of manœuvres whereby a collision situation may be converted into a ‘miss’ of specified magnitude.

‘Inter-Relation of Temperature and Wind on the Route London-New York at 50 mb’ by A. F. Crossley, on page 151 of the April 1969 Journal: Figs 1 and 4 should be interchanged and on p. 156 , line 11, A is the true airspeed.