When the Council invited me to read a paper before the Society they suggested as the subject, “ The Use of Steel in Aircraft.” After some consideration, I came to the conclusion that there was not very much new and interesting to say on the use of steel in structures, but that there was a good deal to say concerning the use of light alloys in special constructions. Not that I claim that what I have to say is new, but the particular use of light alloy sheet to be described certainly merits more consideration than it has so far received in England. It is not to be inferred that I think that the use of steel is likely to decline rapidly, on the contrary, I am of the opinion that it will always be widely used. Everyone seriously, engaged in the technical side of the industry knows that steel of various grades has been used in aircraft from the beginning of aviation amd has been the subject of intensive studies during the last fifteen years. It was obvious from the first that if high stresses could be realised with fair uniformity in the finished structural members—say 35 tons per sq. inch or higher—more economical use of steel on a weight-strength basis could be made than of any other material. However that may be, I shall only touch on steel and its uses in construction at one or two points in the course of the lecture.