772 



THE POPULAR SCIENCE MONTHLY. 



reference to them it is in stable equilibrium, while in regard to 

 side motion its equilibrium is very unstable ; the least thing will 

 upset it. 



To study the matter more conveniently, I have had a form 

 made which eliminates all unnecessary parts and represents only 



Fig. 7. A " Safety " Bicycle, with Lines of Fokce. 



the lines of force and the weight on the saddle (Fig. 8). It con- 

 sists, as you see, of two long, slender pieces of pine, and looks 

 like a huge capital A, the cross-piece serving merely to hold the 

 whole more firmly together. At the apex, A, I have placed a 

 few pounds of lead to represent the rider's weight. 



In the older form of the bicy- 

 cle, the wheel in front is very 

 much the larger. The corre- 

 sponding leg, A B (Fig. 8), is 

 much steeper and shorter than 

 the other. In " safety 'cycles " it 

 is just the reverse, the rear leg 

 being steeper and shorter, while 

 the two wheels are of nearly the 

 same size. As the theory of both 

 C B machines is the same, I shall, for 



Fig. 8. Apparatus illustrating the Way the present, speak Only of the 

 A Bicycle is kept Upright. ~ 



former. 



For convenience in handling, and that it may be better seen, 



I place the foot C, the rear one, on the table, and hold the other, 



B, in my hand, and at the same height from the floor. Now, 



notice : the weight at the apex, or saddle, begins to tilt to the 



