NO. 3 NANtU.FA MEMOTB UN* MECHANICAL FLIGHT 209 



the center of gravity was at (lie point 14!)7, and that, assuming the rear wings 

 to have two-thirds of the lifting effecl of the front ones, the center of pressure 

 was calculated to be at the point 1498, or one centimetre in front of the cen 

 ter of gravity, measured in the horizontal plane. In the vertical plane the cen- 

 ter of pressure was calculated to be at the point 2536, and the center of gravity 

 was found by test to be at the point 2501, when the line of thrust was assumed 

 to be at the point 2500, the center of gravity being actually one centimetre aboi e 

 the line of thrust. 



From the data sheet of Aerodrome No. 6, for its flight of November 28, 

 1896, it will be noted that the line of thrust being at the point 1500 the center 

 of pressure was at the point 1487, and the center of gravity at the point 14S4; 

 that is, the center of pressure was three centimetres in front of the center of 

 gravity, measured in the horizontal plane. In the vertical plane, taking the line 

 of thrust at the point 2500, the center of pressure was at the point 2525, and 

 the center of gravity at the point 2486, the center of gravity being 14 centi- 

 metres below the line of thrust and 39 centimetres below the center of pressure, 

 the distance from the center of pressure to the line of thrust being, therefore, 

 64 per cent of the distance between the center of pressure and the center of 

 gravity. 



As has been explained in Part I, while it is not desirable that the center of 

 gravity be a great distance below the center of pressure, as such a relation 

 tends to produce a special kind of rolling and pitching in varying currents of 

 air, it is highly desirable that the center of gravity should lie some distance 

 below the line of thrust in order that the three forces may be balanced. In a 

 macnine like model No. 5, where the center of gravity was actually, though 

 very slightly above the line of thrust, there is a constant tendency to produce 

 rotation of the aerodrome, if for any reason its equilibrium is disturbed, which 

 is corrected in practice by the action of the Penaud tail. In model No. 6, on 

 the other hand, the disposition of the three factors was such that they tended 

 to maintain, rather than to destroy, the initial equilibrium of the machine. 



These desirable relative positions had been made possible in model No. 6 

 by the fact that the center of gravity and line of thrust could be located at 

 practically any desired point, since with the use of steam the power plant con- 

 sists of two separable parts, the boiler, with its fuel and water tanks, and the 

 engine. These parts can, therefore, be placed in any part of the aerodrome that 

 constructional or theoretical reasons demand. Furthermore, the engine consti- 

 tutes such a relatively small portion of the weight of the entire machine that, 

 if for any reason it is desirable to place the engine in the same plane as the 

 line of thrust, its weight is not sufficient to alter materially the position of the 

 center of gravity, since the boiler, water and fuel tanks can be placed as low 

 as desirable and connected with the engine by suitable pipes. 



