My flight from List, Germany, to Chicago, via Greenland and Labrador, was made in July and August of 1931. I had previously made a similar flight to America in 1930 when I chose the south point of Greenland and became very much impressed by this magnificently interesting country. Ever since that flight I had a strong desire to explore this country more closely. My desire for a second flight became acute when we, in Germany, received the first reports of the British Arctic Air-Route Expedition, under the leadership of Mr. Watkins.

Their weather reports for our prospective flight were very favourable and I immediately set to work to organise my second venture.

I wish to make it quite clear that any opinion expressed in this lecture is merely a personal opinion, and does not tend in any way to express the official view.

As a serving officer it has been necessary for me to obtain permission to give this lecture, and a copy of the proposed lecture has been submitted to the authorities, but this in no way implies that they are in agreement with the opinions expressed in the lecture.

The control of an aeroplane is effected through the medium of three distinct sets of control surfaces known as the elevators, ailerons, and rudder, these surfaces being so disposed with reference to the centre of gravity of the machine as to be capable of producing rotation about three mutually perpendicular axes passing through this point, and called the lateral, longitudinal, and normal axes respectively. Thus, the elevators cause a rotation about the lateral axis of the machine, the resulting motion being known as pitching, the ailerons a rotation about the longitudinal axis, producing rolling, and the rudder rotation about the normal axis, producing yawing.

If I wish to know the load which a structure will support without yielding or breaking, or its deflection under some load, I usually make calculations embodying numbers representing certain properties of the materials used, determined by some simple experiments. Sometimes the mathematics may be exceedingly difficult, or even intractable; or the mathematical solution may be achieved only at the expense of assumptions whose validity seems to need confirmation. I may then experiment with my structure, full scale; but it may be large and costly and I may wish to know the answer before I venture to build it. I may make a small scale model and experiment with that.