92 MECHANICAL RECREATIONS [CH. V 



pencil will raise the centre of gravity of the whole : thus the 

 equilibrium is stable. 



Other similar tricks are the suspension of a bucket over 

 the edge of a table by a couple of sticks, and the balancing of 

 a coin on the edge of a wine-glass by the aid of a couple of 

 forks* — the sticks or forks being so placed that the centre of 

 gravity of the whole is vertically below the point of support 

 and its depth below it a maximum. 



The toy representing a horseman, whose motion continually 

 brings him over the edge of a table into a position which seems 

 to ensure immediate destruction, is constructed in somewhat 

 the same way. A wire has one end fixed to the feet of the 

 rider; the wire is curved downwards and backwards, and at 

 the other end is fixed a weight. When the horse is placed so 

 that his hind legs are near the edge of the table and his fore- 

 feet over the edge, the weight is under his hind feet. Thus 

 the whole toy forms a pendulum with a curved instead of a 

 straight rod. Hence the farther it swings over the table, the 

 higher is the centre of gravity raised, and thus the toy tends 

 to return to its original position of equilibrium. 



An elegant modification of the prancing horse was brought 

 out at Paris in 1890 in the shape of a toy made of tin and in 

 the figure of a manf. The legs are pivoted so as to be movable 

 about the thighs, but with a wire check to prevent too long 

 a step, and the hands are fastened to the top of a fl -shaped 

 wire weighted at its ends. If the figure is placed on a narrow 

 sloping plank or strip of wood passing between the legs of the 

 fl, then owing to the fl -shaped wire any lateral displacement 

 of the figure will raise its centre of gravity, and thus for any 

 such displacement the equilibrium is stable. Hence, if a slight 

 lateral disturbance is given, the figure will oscillate and will 

 rest alternately on each foot : when it is supported by one foot 

 the other foot under its own weight moves forwards, and thus 

 the figure will walk down the plank though with a slight 

 reeling motion. 



* Oughtred, p. 30; Ozanam, 1803 edition, vol. n, p. 12; 1840 edition, 

 P- 199. f La Nature, Paris, March, 1891. 



