The invitation which you, Mr. President, were good enough to issue to me some months ago really amounted, I am afraid, to a request that I should come here to prophesy. My reply was that it was not possible, or at any rate, I did not propose to undertake it. All one could do was to follow the recent development of materials for aircraft purposes as well as possible in order to see the general tendencies of that development and those which seemed likely to be followed in the near future. But even with regard to that limited degree of forecasting, I must warn you that it is undertaken with every possible reservation, and for this reason, that while one may be able to foresee to a certain extent a number of feasible lines of advance, there have always been in the past history of all branches of technology unexpected developments which no man could foresee, and which I personally make no pretence of being able to visualise. Therefore I would ask you to look with more confidence on what I have to say about what has been and what is, than about what may be.