The Force of the Breath.
When you blow into a paper bag in order to swell it out, afterward bursting it with a blow to produce the familiar “bang,” have you ever stopped to ask yourself what was the precise force of your breath? You know that such force can be measured by the instrument known as the spirometer, which you occasionally see at a railway station or a country fair. But a simple paper bag may be made to answer the purpose of the spirometer, as I propose to explain.
The bag must be rather long and narrow, airtight, and of thin, tough paper. A bullock’s bladder will answer the purpose still better. A tube should be inserted in the neck, through which to blow. Lay it flat, near the edge of a table, with the mouth turned toward yourself; place various weights upon it, increasing by degrees, and you will be surprised at the weight that your breath will thus lift. To upset a couple of big dictionaries, placed one upon the other, will be mere child’s play, as you will find on putting the matter to the test.