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.

At the end of 1915 I was invited to compile and deliver a course of lectures on the Theory of Ballooning at the Royal Naval Air Station at Roehampton; and for the following three years I attended regularly at Roehampton, delivering two lectures daily and setting examinations for the officers under instruction to pass into the Airship service and into the Kite-Balloon Service.

Every encouragement was given for questions to be asked on aerostatic problems after each lecture, my endeavour being to remove as many troubles in the minds of probationers as possible. The trouble which stood out above all others soon became apparent. What would happen to the observers in a kite-balloon in the event of the cable breaking owing to a high wind or to its being shot through? The questions put to me showed this to be the chief cause of anxiety, and it will be seen that the causes for this anxiety were well founded.