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.
Through the Water Dry.
Into a basin full of water, throw a coin, or ring, or other suitable object, and announce that you will take it out of the basin without wetting your hand. All that is needed to effect this is to dust the surface of the water with some form of powder having no cohesion with water, and which, consequently, water does not moisten. Powdered lycopodium, to be procured of any chemist, has this property.
Having sprinkled a little of this powder on the surface of the liquid, plunge your hand boldly to the bottom, pick up the ring, and show the company that your hand is as dry as it was before the operation. This comes of the fact that the lycopodium has formed over your hand a regular glove, to which the liquid cannot adhere any more than it can to the plumage of the ducks, which we see plunge and plunge again, and still come up dry as ever, by reason of the oily matter secreted by their feathers.
Those who may care to carry the experiment further may try it with hot water, increasing the temperature at each attempt, when they will find that it is possible, with the aid of the lycopodium, to lift an article out of a kettle of all but boiling water. The sensation of heat is not destroyed, but it causes no injury to the tissues—in other words, no scald.