In the Paper which I read before the Äeronautical Society, at the General Meeting in 1878, I stated that; with respect to those of my models which are actuated by wing–movement, I had found a difficulty of sustaining the weight which appertains to the living example. But, from experiments which I have lately made, I find that the weight to be sustained depends upon power and strength of material employed, and also upon the right application of that power. For instance, in the wing–action of the bird, that portion of the pectoral muscle which depresses the wing is considerably more powerful than that which elevates it, because its functionis to sustain the whole weight of the bird by impact upon the air. In my models I attain that action by affixing india–rubber cord, more or less in tension (according to the powerused), underneath the wings, so that when the wings are elevated there shall be a strong downward impetus.