It is a very great honour to me to have to speak this evening before this learned assembly, and I have to thank you very sincerely for the occasion which you have offered me of discussing before you a very important question, one which is of interest to the whole of the aeronautical world, namely, the problem of the helicopter.

My aim will be but modest, for I shall simply attempt to develop those essential arguments which have given me such entire confidence in the practicability of this type of heavier-than-air machine, and I shall be content if at the end of this paper I have been able, not to convince you, but at least to interest you in the cause which I have at heart.

The helicopter is not a competitor of the aeroplane. It is an entirely different type of aircraft, but the one is the complement of the other, and if their respective uses are not the same, they nevertheless will be of equal importance in that immense future which we all believe to be reserved for aircraft.

The following note has been written partly by way of a commentary upon Dr. H. C. Watt's recent article, in the July number of the Aëronautical Journal, entitled, “ A Note on the Theories of Screw Propulsion,” and partly by way of an explanation of the apparent inconsistency of the “inflow” theory of the airscrew.

Consider an element of a propeller blade situated at a radius of x from the boss centre of the propeller and having an angle of ϕ between the chord line of the blade section and the plane of rotation. The form of the blade section is considered to be that of an aerofoil, of which the characteristics are known from wind channel experiments upon a model of the same geometrical form (Fig. I).

We wish to apply these wind channel data to the propeller blade element with rigorous consistency, i.e., as far as the two respective régimes of the propeller and the aerofoil permit.

The weather of the English Channel and South East Coast of England, like that of other localities in the British Islands, is well known to be variable and subject to rapid changes which take place sometimes with little or no warning. These changes are in places complicated by such factors as the general contour of the cliffs, an abrupt fall of the land towards the south, and the effects of evaporation taking place continuously over the channel, and giving such a well defined local character to changes of wind as to mask temporarily the indications of an approaching disturbance.

Much, however, can be ascertained by the study of the local cloud formation, wind structure, type of barometric curve, and temperature variation, and the following discussion of certain aspects of Channel meteorology is intended to explain the commoner variations of weather which occur in that area. The meteorological peculiarities of the Channel may be conveniently studied under the six separate headings of atmospheric depressions (primary and secondary), winds, mist and fog, thunderstorms, squalls and gales.