[Illustration]
By another variation of the conditions it is possible to balance the pin
upon the needle-point in a horizontal position and to make it revolve
thereon in that situation. The only alteration necessary to the
preparations already made is to substitute for the two forks two
ordinary pocket-knives. By bending the handles of the knives at an angle
to the blade, the pin may be sustained in a horizontal position. Or, by
the substitution of a long needle for the pin, the forks may be retained
as balance-weights, as in the previous example and as shown in the
present illustration. The pin may be rested upon the needle-point as in
the figure, and by a gentle touch of the finger may be set revolving. In
time, by reason of the relative differences in hardness of the two
metals, the commencement of a tiny hole will be drilled by the sharp
steel point of the needle in the softer brass of the pin, and if the
motion be continued for a sufficient length of time a hole will
ultimately be an accomplished fact.