Before proceeding, I wish to say that I much appreciate the invitation to present this paper to your Society. The science of aeronautics has evolved at a great pace, and typifies what can be done with applied science, and the tangible results are so apparent that it would be superfluous to discuss them. It would appear to me that the rapidity with which the efficiency has increased is due to the whole-hearted collaboration of the different branches of applied science and engineering, the honours being shared after giving first place 10 the sportinginstinct of the early flyer, by the physicist, the engineer, and the metallurgist. You will notice that my modesty places the metallurgist last. It is quite a confession to make, but it is a fact, nevertheless, that I accepted with pleasure your invitation to give this paper, principally because I have always taken a keen interest in the metallurgical side of aeronautics.

1. The object of this paper is to explain the principles upon which the flapping flight of birds depend and to show how the velocities, power expended and gliding angles can be approximately calculated. The birds are considered to be flying on a horizontal course with constant velocity. The calculations have been made for five birds, the Teal, the Grouse, the Common Swift, the Starling and the Stork, but the formulae given can of course be used for any bird.

2. The results obtained seem to show that:—

1st.—As regards velocities, the very high speeds given by some writers are by no means so impossible as is generally supposed.

2nd.—The power expended at these high speeds is much less than the estimates usually made.