1. 1. I have recently paid a visit to Egypt and Mesopotamia with the object of finding out the particular troubles that are experienced with aeroplanes and engines in tropical climates. My stay in those countries only lasted for a total of 41/2 weeks in July and August, and that, of course, is quite an insufficient time to get complete knowledge of the subject. In many cases I am afraid the information I shall give will be somewhat indefinite, but my main object is to indicate the troubles and leave their solution to other people.

2. 2. First as regards the climatic conditions. The general impression I got was that, as regards the effect on aircraft materials, Mesopotamia was very nearly as much worse than Egypt as Egypt is than England, so that although one may get a solution for a particular difficulty in Egypt, it does not necessarily follow that the same solution will get over the difficulty in Mesopotamia.

An earlier article dealt with so many matters in connection with wire cables that it was possible to pay but scant attention to sockets. A socket is a neat, light and convenient form of end connection for a cable. It is widely employed in general practice, but its use in connection with aircraft appears to have been confined to airships. The photograph shows different types and sizes of sockets viewed in several directions.

Introductory.—In the course of inquiries made recently by the Accidents Investigation Sub-Committee they were impressed by the fact that the various terms normally used to describe the characteristics of an aeroplane in regard to its stability or instability are incomplete and defective from a pilot's point of view. Not only did there appear to be differences in the meanings attached to the various stability terms by pilots and others, but in several cases the meanings were not in accordance with the definitions used in physical science generally. It appeared that a scheme of definitions could be drawn up which would be acceptable both to those interested practically and theoretically in the subject. Definitions are needed for discussions on stability and particularly in making more definite the information given by pilots when describing the behaviour of aeroplanes. It is felt that the definitions, if accepted on all hands, would lead to such observations during the life of an aeroplane as materially to assist the investigations of accidents.

I feel it a great honour to whave been asked by this Society to speak to you this evening on this subject. The question of the utilisation of airships for commercial purposes has attracted an immense amount of public attention during the past year. Unfortunately, owing to the high costs of running airships experimentally, the Air Ministry have been faced during this period with the necessity of having to abandon airships for military purposes, and also of having to cease their experiments on the use of these ships for commercial purposes. Fortunately it is inherent in the British temperament to give its greatest sympathy to a man when he is down, and for this reason, concurrently with the complete cessation of all airship activities, such stupendous ideas as the use of airships for linking up the Colonies have been put forward. The scheme for using aircraft on such an unprecedented scale for commercial purposes is so gigantic as to call for very grave and careful consideration.