attached, 65 35. The little steam engine used by me in my rotating arm experiments, 66 36. The machine attached to the end of the rotating shaft, 68 37. Marking off the dynamometer, 69 37_a_. Right- and left-hand four-blade screws, 70 38. Apparatus for indicating the force and velocity of the wind direct, 71 39. Apparatus for testing the lifting effect of aeroplanes, 73 40. Front elevation of proposed aeroplane machine, 77 41. Side elevation of proposed aeroplane machine, 78 42. Plan of proposed aeroplane machine, 79 43. Plan of a hélicoptère machine, 82 44. Showing the position of the blades of a hélicoptère as they pass around a circle, 83 45. System of splicing and building up wooden members, 86 46. Cross-section of struts, 86 47. Truss suitable for use with flying machines, 87 48. The paradox aeroplane, 88 49. The Antoinette motor, 89 50. Section showing the Antoinette motor as used in the Farman and De la Grange machines, 90 51. Pneumatic buffer, 91 52. Gyroscope, 94 53. Adjusting the lifting effect, 95 54. Showing that the machine could be tilted in either direction by changing the position of the rudder, 96 55. Adjusting the lifting effect, 97 56. Adjustment of the rudders, 98 57. Diagram showing the evolution of a wide aeroplane, 102 58. In a recently published mathematical treatise on aerodynamics an illustration is shown, representing the path that the air takes on encountering a rapidly moving curved aeroplane, 104 59. An illustration from another scientific publication also on the dynamics of flight, 104 60. Another illustration from the same work, 105 61. The shape and the practical angle of an aeroplane, 105 62. An aeroplane of great thickness, 106 63. Section of a screw blade having a rib on the back, 106 64. Shows a flat aeroplane placed at an angle of 45°, 107 65. The aeroplane here shown is a mathematical paradox, 107 66. This shows fig.