8 IMPENETRABILITY. 



these bodies. From this it appears that the substance 

 or matter, of which bodies consist, fills space in such a 

 manner that no other body can at the same time 

 occupy the same portion of space. This property of 

 matter is called impenetrability. It is common to all 

 kinds of matter, even to air, although it is not so appa- 

 rent in this body as in others, because air is invisible, 

 and may be displaced without sensible effort. But if a 



FIG. 8 (| real size]. FIG. 9 (| real size). 



tumbler,, which in the usual meaning of the word is 

 empty, be inserted mouth downwards, as shown in 

 fi'g. 8, "into a jar containing water, the water will 

 jiot .enter the tumbler, because the air which filled it 

 previously cannot escape. We observe, on the con- 

 trary, that the water in the larger vessel gives way 

 before the air which is compressed in the tumbler, and 

 rises in the jar, or runs over if the jar was full at first. 

 When we fill a bottle with water, the air usually 

 escapes freely ; but if a funnel with a narrow tube be 

 fitted air-tight into the bottle by means of a perforated 

 cork (fig. 9), it will be impossible to fill the bottle 

 because the air cannot escape. It will, however, be 

 found in this and in the last experiment, that a small 

 quantity of water will enter the tumbler or the bottle ; 



