Tie a thin piece of light indiarubber round the top of the bottle, and you will notice that as the air is withdrawn, the indiarubber will stretch, and at length form a round small balloon in the interior of the bottle. (Fig. 1).

If a piece of bladder is tightly stretched and tied round the vessel (fig. 2.) it will burst under the force of the atmospheric pressure which acts upon it, through a vacuum having been made underneath. This is another case of the first experiment with the air pump described above.