Balloons, 120 „ spiders, 27 Birds as thermo-dynamic machines, 153 „ Two classes of, 23 Bleriot’s machine, 113 Boiler experiments, 156 Brayton’s gas engine, 154 British war balloon, 159, 162 Building up of my large screws, 41 Burner employed in my experiments, 157 Character of text-books recently published, 1 Circulation of air produced by differences in temperature, 27 Cody’s kite, 28, 30 Comparative value of different motors, 151 Conclusions regarding air currents, 21 Condensers, Testing of, 52 Condenser tubes, 60 Continental flying machines, 9 Crystal Palace experiments, 72-76 Darwin on the flight of condors, 11 Deflection of air coming in contact with aeroplanes, 2 De la Grange machine, The, 110 “Dirigible” No 2, 159, 162 Drift at various distances from center to center, Table of, 58 Dynagraphs, 136 Dynamic energy of animals, 127