Eagles, Flight of, 19 Efficiency of screw propellers, 147 „ screws in steamships, 47 Energy developed by a bird, 13 Engines, 153 Equivalent inclinations, 115 „ velocities, 116 Experiments of Count Zeppelin, 124 „ Horatio Philipps, 9, 118, 119, 145 „ Lord Rayleigh in reference to Newton’s Law, 6 „ Professor Langley, 9, 62, 99, 109 „ Wright Bros., 109 Experiments to show efficiency of Screw propellers, 33 „ with apparatus attached to rotating arm, 62 „ „ boiler, 156 „ „ hard rolled brass aeroplane, 3 „ „ my large machine, 10, 133 „ „ rotating arm, 64-72 „ „ small machines attached to rotating arm, 159 Fabric covered screw, 40 Farman’s machine, 110 Flying of kites, 25, 28, 29 Forced circulation used by me, 158 Formulæ unsupported by facts, 3 French and English measurements, 128, 129 Gulls, 20, 21 Gyroscope apparatus, 93 „ Steering by means of, 92 Hawks and Eagles, 13 Hélicoptère machine, 82 Hints as to the building of flying machines, 77-91 Horizontal movement of the air, 14 Hub for flying machine, New form of, 45 Interstellar temperature, 15 Introductory, 1 Kites, 21, 22, 25, 26, 28, 29 „ Behaviour of, 26 „ Flying of, 25, 28, 29