LIVING IN AN OCEAN OF AIR 



or, in fact, at the bottom of it. We know that it surrounds 

 us, for does not moving air turn our windmills, blow off our 

 hats, blow out lights, uproot trees, and even wreck houses 

 and whole settlements at times ? 



We know that air occupies space, for if we force an 

 " empty " glass upside down into a pan of water, we find 

 that the water does not 

 enter the " empty " space. 

 We know that air is capable 

 of holding things up. It 

 pushes against our kites. It 

 holds up balloons. It even 

 holds up the moving heavier- 

 than-air machines, or air- 

 planes. The first man who ever flew in an airplane took his 

 simple machine to the crest of a hill, up which a strong wind 

 was blowing. He then launched the glider, for there were no 

 motors used at first in the air, and the force of this air 

 against the flat wings of the machine held him up for a time. 



We may see further evidence that air is a real substance 

 by performing the following experiment. 



Is the glass really empty ? 



Clccnv-p 



Experiment. To show the re- 

 ality of air. 



Materials: Eight-ounce 

 wide-mouth bottle. Two- 

 hole rubber stopper. 

 Funnel. Glass tube. 

 Rubber tube. Clamp. 

 Beaker. 



Method : Arrange the ap- 

 paratus as in diagram. 



Observations and Conclu- 

 sions : When the clamp is 

 closed why does the 



