77 o THE POPULAR SCIENCE MONTHLY. 



larger the radius the smaller the centrifugal force. If the radius 

 of curvature becomes infinite i. e., the curve becomes a straight 

 line the centrifugal force becomes infinitely small, or zero. 



So long, therefore, as the bicyclist does not turn corners keeps 

 in a straight course the centrifugal force gives us no assistance 

 whatever in understanding why he keeps his seat so securely. 

 But yet it may be thought that this force, if supplemented by 

 skillful balancing, is sufficient. It keeps the bicycle from falling 

 when turning corners : will not good balancing account for the 

 stability when moving in a straight course ? We are all familiar 

 with the phenomena of balancing one's self. "We know the help 

 a heavy pole gives at such times ; how a person's legs and arms 

 move with startling rapidity in the opposite direction to that in 

 which he feels himself falling. There is nothing of this on the 

 wheel. If the stability was due to balancing, it would not be so 

 very difficult for a bicyclist to sit upon his machine when not in 

 motion., and when its wheels both point in the same direction. I 

 have never seen one that could do it. I suspect, however, that it 

 is not impossible, any more than to stand on the top round of an 

 unsupported ladder. But the ordinary bicyclist can not do it ; 

 and yet, without apparent effort, he rides securely. That his sta- 

 bility is not due to his balancing and to his rapid forward motion 

 combined, is evident when we reflect that if the handles are made 

 immovable, so that neither of the wheels can be turned to the 

 right or left, it is impossible for any ordinary rider, no matter at 

 what speed he may move, to keep from falling for any consider- 

 able time after he once begins to tilt. 



Apparently the fact that some can ride " hands off " on a safety 

 wheel contradicts this, for, however it may be on an " ordinary/' 

 on a " safety " the rider can not guide it by the pedals, and as he 

 does not touch the handles of the steering-wheel or the wheel 

 itself, it would seem that his not tilting must be due to good bal- 

 ancing. Experiment, however, proves the contrary. Let the 

 steering-wheel be fixed by tying the handles, or by a clamp on 

 the spindle, so that it can not turn to the right or the left, and 

 then let the 'cyclist try to keep it erect. Balancing won't help, 

 except possibly to delay his fall a few moments. And worse than 

 that, he can't ride hands off at all if he tries to do so only by bal- 

 ancing. The explanation of such riding is not very difficult, but 

 requires some other matters to be treated first. At present all I 

 desire to establish is that in this kind of riding, as well as in all 

 others, the rider's ability to keep from falling to one side for an 

 indefinite time while traveling in a straight line is not due to bal- 

 ancing. 



I think you will agree with me that the reasons thus far 

 assigned for the stability of the bicycle cast little or no light 



