Experimental glass blowing for boys

by Carleton John Lynde

FIG. 102
TUMBLER PENDULUM

Experiment 78. A magic pendulum.

Pass a string through a small hole in a piece of cardboard, knot the end of the string, and drop melted candle wax over the hole to make it air tight.

Fill a tumbler with water, press the cardboard down on the tumbler with the palm of your hand, and lift the string. Do you also lift the tumbler (Fig. 102)?

Swing the tumbler gently as a pendulum.

FIG. 103
POULTRY FOUNTAIN

Experiment 79. A poultry fountain.

To make the poultry fountain (Fig. 103), fill a bottle with water, hold your thumb over the mouth, invert the bottle over the pan of water, and remove your thumb under water. Does the atmospheric pressure on the water in the pan hold the water in the bottle?