When some twenty-five years ago I began making notes of the effects of altitude on the human animal, I never dreamt I should be called upon to make public any of my observations; I am doing so now with the utmost diffidence and buoyed up by the hope that a few of the facts I am about to bring to your notice may be even indirectly useful.

In view of the rapidly approaching use of commercial aviation as a means of passenger transport, I wish it to be clearly understood that I am not approaching the subject from the purely scientific point of view, but rather from the standpoint of the men in the street, whose experience of altitude may be very moderate, as indeed is my own.

The undercarriage is described in the Society's Glossary as “That part of the aircraft beneath the body intended for its support on land or water and to absorb shock on alighting.”

It is my intention to confine my remarks in this paper to undercarriages designed to support aircraft on land, that is to say, colloquially, “landing gears.” The reasons for this limitation are obvious; it is scarcely possible to compare even in a general manner the undercarriage problem of the land machine and the seaplane, and in the latter case the already wide subject has to be extended to consider float design.

The historical development of the undercarriage shows well-defined phases reflecting the performances and functions of the complete aircraft. In the early Wright machines, which were provided with a launching gear, the problem of alighting only required to be considered.

Let me commence with an explanation and an apology. About a year ago we were discussing the Annual Report of the Advisory Committee for Aeronautics for 1918é19, and I suggested that in that report was ample material for an interesting Paper dealing in great measure with advances during the war; material which up to then had been strictly confidential in character. Some few months ago an invitation came to me from your Council to read such a Paper, and I hastily accepted.

Six weeks ago I sat down to put my ideas in form and wrote some few pages when it suddenly occurred to me that Prof. Bairstow, in his Wilbur Wright lecture last year, had dealt with the subject in a most able and complete way and with very full knowledge, and that I had but little to add to his admirable exposition.