Our readers have often seen grocers' clerks or employes of business
houses break the string with which they had tied up a package, by seizing
it with the hands, bringing the latter close together, and then suddenly
separating them with a quick movement. If it be thought that this quick
motion is sufficient, let any one try it, and he will merely cut his
hands without breaking the string, provided the latter has some little
strength. In order to succeed, the cord must be arranged in a certain
manner, as we shall explain.
[Illustration: MODE OF BREAKING A CORD WITH THE HANDS.]
The cord to be broken is placed upon the left hand, and one of its ends
is passed over the other in such a way as to form a cross, and the end
forming the shorter part of the cross is wound around the fingers (it
should be left long enough to make several turns). The other end is then
turned back and wound around the right hand, so as to leave a space of
about eighteen inches between the latter and the left hand. If these
directions are properly followed, the string should have the form of a Y
in the middle of the hand, as shown in the lower figure of the
accompanying engraving.
It is only necessary after this to close the hand, after seeing that the
Y is very taut, and to seize the cord with the other hand, as shown in
the upper figure. This done, the two hands are brought together and then
suddenly separated so as to give a quick pull on the point of junction of
the Y-shaped branches, which form a true knife. It will be readily seen
that as the cord is broken suddenly the shock does not have time to
transmit itself to the hands. This is an interesting demonstration of the
principle of inertia.
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