THE PROPERTIES OF MATTER. 



the other cork lead a tube to the water-pan, and let it 



terminate beneath or 

 within the neck of 

 a clear glass bottle 

 filled with water, 

 and inverted in the 

 water-pan. See that 

 the corks are air- 

 tight; if necessary, 

 seal them with wax 

 or plaster of Paris. 

 If a two-necked bot- 

 FlG - 2. tie be not convenient, 



substitute therefor a 



wide-mouthed bottle having two holes through the cork. 

 The delivery tube is best made of glass. It may be easily 

 bent by first heating it red-hot in an alcohol or gas flame. 

 Pour water steadily through the funnel ; as it descends, 

 air is forced out through the delivery tube, and may be 

 seen bubbling through the water in the inverted bottle. 

 At the end of the experiment, the volume of water in the 

 two-necked bottle will be nearly equal to the volume of air 

 in the inverted bottle. This clearly shows the impene- 

 trability of air. 



33. What is Weight ? Weight is (as the term 

 is generally used) the measure of gravity or molar at- 

 traction ( 7) of which it is a necessary consequence. 



(a.} As all masses of matter exert this force, weight necessarily 

 pertains to all matter ; but, in general use, the term weight has 

 reference to bodies upon the earth. If a body be placed near the 

 earth's surface and left unsupported, the mass-attraction of the 

 earth for each molecule in the body will draw the two together, and 



