ee
of these arms may have to be made before one is secured that is of
the exact proportions to catch the vibrations right.

[Illustration: How to Cut the Notches]

To operate the trick, grip the stick firmly in one hand, and with
the forward and backward motion of the other allow the first
finger to slide along the top edge, the second finger along the
side and the thumb nail will then vibrate along the notches, thus
making the arm revolve in one direction. To make the arm revolve
in the opposite direction--keep the hand moving all the time, so
the observer will not detect the change which the band
makes--allow the first finger to slide along the top, as in the
other movement, the thumb and second finger changing places: e.
g., in the first movement you scratch the notches with the thumb
nail while the hand is going from the body, and in the second
movement you scratch the notches with the nail of the second
finger when the hand is coming toward the body, thus producing two
different vibrations. In order to make it work perfectly (?) you
must of course say "skidoo" when you begin the first movement, and
then, no matter how fast the little arm is revolving when changed
to the second movement, you must say "skidee" and the arm will
immediately stop and begin revolving in the opposite direction. By
using the magic words the little arm will obey your commands
instantly and your audience will be mystified. If any of your
audience presume to dispute, or think they can do the same, let
them try it. You will no doubt be accused of blowing or drawing in
your breath, and many other things in order to make the arm
operate. At least it is amusing. Try it and see.
--Contributed by Charles Clement Bradley, Toledo, Ohio.

* * * * * * *

The foregoing article describing the "Skidoo-Skidee Trick"
appeared in a recent issue of Popular Mechanics. I have been told
that a similar arrangement is used by a tribe of Indians in the
state of Washington, by the Hindoos in India, and one friend tells
me that they were sold on the streets of our large cities many
years ago.

This toy interested me so much that I have made an investigation
into the causes of its action, and I think the results may be of
interest.

To operate, one end of the notched stick is held firmly in the
left hand, while with the right hand a nail or match stick is
rubbed along the notched edge, at the same time pressing with the
thumb or finger of