The Rotation of the Globe.
When you next chance to eat an egg for breakfast, do not fail to try the following experiment. It is one which always succeeds, and is productive of much amusement to the company.
Moisten slightly with water the rim of your plate, and in the centre paint with the yolk of the egg a sun with golden rays. By the aid of this simple apparatus you will be in a position to illustrate, so clearly that a child can comprehend it, the double movement of the earth, which revolves simultaneously round the sun and on its own axis.
All that you have to do is to place the empty half-shell of your egg on the rim of the plate, and keeping this latter duly sloped, by a slight movement of the wrist as may be needful, you will see the egg-shell begin to revolve rapidly on its own axis, at the same time traveling round the plate. It is hardly necessary to remark that the egg-shell will not travel uphill, and the plate must therefore be gradually shifted round, as well as sloped, so that the shell may always have an inch or two of descending plane before it.
The slight cohesion caused by the water which moistens the plate counteracts the centrifugal force, and so prevents the egg-shell falling off the edge of the plate.