156 THE THEORY OF THE BICYCLE. 
quickly towards the west. In every case by moving my 
hand more rapidly than the weight tilts, I bring the 
point of support under it. It is very easy in this way to 
keep it from falling. 
But how can the rider move the point of support when 
it is on the ground, several feet out of his reach 2 
He does it by turning the wheel to the right, or left, 
as may be necessary, that is by pulling the cross-bar to 
the right or left, and thus turning the forked spindle 
between whose arms the forward wheel is held and 
guided. 
But some one will ask, How does turning the wheel 
bring the point of support to the right or to the left— 
which ever way the machine may be tilting ? 
Let us suppose a ’cyclist mounted on his wheel and 
riding, say, towards the north. He finds himself begin- 
ning to tilt towards the right. He is not only going 
north with the machine, but he is going east. He turns 
the wheel eastward, the point of support at once begins 
to go eastwardly, and as it goes much faster than the 
machine tilts—at first—it quickly gets under him, and 
the wheel is again upright. To one standing at a dist- 
tance, in front or rear, the bottom of the wheel will be 
seen to move to the right or left, just as a few moments 
ago, I moved the foot of the frame which I exhibited. 
Here then we have the explanation sought. The sta- 
bility of the Bicycle is due to changing the direction of 
the wheel to the right or left, which ever way the leaning 
is, and thus keeping the point where it rests on the 
ground, under the rider. 
It may be questioned whether the bottom point of the 
wheel really travels faster than the weight at the saddle 
tilts over, and, if it does not travel faster, the explana- 
tion which I have been giving fails. This can readily be 
answerel. By an easy calculation based on the principle 
‘well known in physics, that the velocity of a body moving 
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