148 THE THEORY OF THE BICYCLE. 
on examination, I found that, of the several pages of 
closely-printed matter, the ‘‘theory ’’ occupied possibly 
a dozen lines, all the rest was about the bicycle, but not 
about its theory. 
In those dozen lines we are told that Mr. Boys ex- 
hibited a top in action, and requested his audience to 
notice its remarkable stability. Then he said that the 
stability of the bicycle was due to the same principles, 
but made no attempt to show any connection between 
them. 
The top revolves on its axis, and it stays up, as you 
see ; the wheel of the bicycle revolves on its axis, there- 
fore it stays up, was his theory and demonstration, and 
the whole of it, and so far as we can judge from the re- 
port, he was satisfied, however it may have been with his 
audience. | 
Of all machines, probably none is so little understood 
as the top, and its near relative, the gyroscope. Hence 
the best that can be said is, that the lecturer merely 
availed himself of that tendency, found in most minds, 
to explain an unfamiliar phenomenon by referring it to 
some other more familiar phenomenon, longer known, 
but equally incomprehensible. As if, as in grammar 
two negatives make an affirmative, so, in physics, two 
unknowns make a known. 
Without going into the theory of the top,—the gyro- 
scope, it is easy to show that their stability, and that of 
the bicycle must be due to different 
principles. I spin before you on the 
table a top with a somewhat blunt 
point. You notice that it runs around 
in a circular, or spiral path, and gradu- 
ally rises till it is perpendicular to the 
table. I strike it quite a hard blow, but do not up- 
set it. In fact it is hardly possible to strike it with force 
enough to upset it. I send it flying across the table, 
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