Prior to 1914 there was no night flying proper, as we know it to-day, and therefore, so far as I am aware, there was no night lighting. I must except, of course, the night flying exhibitions which were given at Hendon in this country and at a few places abroad.

One of the routine ground tests carried out on pressurised aircraft is the measurement of the leakage rate and this is often expressed in the form of a time for the cabin excess pressure to fall from a given value to half that value. The technician, however, is usually concerned with the functioning of the pressurised cabin at high altitude and it is the purpose of this note to establish a means of forecasting the high altitude performance from the sea level test. The first part of the note describes the basic theory and provides a unique relationship connecting leakage times at any height with that pertaining to the sea level test. The latter part of the note gives an example of the use of this information in predicting the fall off of cabin pressure after pressurisation failure and with the aircraft descending.

In the later part of autumn last year, I was invited by your President, Colonel the Master of Sempill, to read a paper about the work of the “ Deutsche Versuchsanstalt fur Luftfahrt ”( i.e. “ German Aeronautical Research Institute ” ) . The Royal Aeronautical Society can look back to a long and successful development. Your Society has always aimed at the promoting of the technical work of your country and at the fostering of close scientific relations between air–minded countries. It is therefore a great honour for me to lecture before your Society.

I regard co–operation in discussing areonautical matters between the various countries as very necessary. Representatives of aeronautical science have, during the past year, held international congresses at Stockholm, in the Hague and finally in Paris. Common problems were treated at these congresses by the representatives. New personal relations were formed during the meetings held there.

The subject of statistics is so vast that many thousands of volumes have been written on it and it would be lunacy to try to give any complete outline in a brief paper. Even by confining the field to that range of data arising from aeronautical engineering the limit seems to recede into specialist abstractions rather than narrow as generality is jettisoned. At the outset it may be well to consider these apparent platitudes because many (most?) otherwise well-informed people are dogmatic in their belief that statistics are merely applied arithmetic. No doubt the same kind of thing was said before any distinction was drawn between a tally-clerk and a qualified accountant. The assertion contains too much fundamental truth for easy rebuttal: nevertheless there does exist both a science and an art in statistics, and arithmetic is only one important contribution to the exercise of either.

Since the vaiious nations definitely set out upon the course of aeronautical armaments, the problem of the organisation of this new service has arisen, and appears to present serious difficulties if it should be necessary to effect periodical changes and modifications or at least substitutions in personnel.

This uncertainty is due partly to the fact that quite new questions are being dealt with; partly to the erroneous process of enforcing upon the new fighting service the rules of the older ones—the army and navy; and in a larger measure to the practical difficulties which have to be faced at every turn in passing from the theoretical field to the actual.

In the following pages an attempt is made to present the chief problems which arise in the aeronautical field, so as to form an idea for their solution, adducing opinions frequently diverse and antagonistic which the experts maintain in their respective arguments.