THE REASON WHY. 



195 



1 Hear, ye children, the instruction of a father, and attend to know under- 

 standing.." PBOVEKBS IV. 



854. Why does the pressure applied to the handle of an 

 air pistol propel the cork? 



.Because, between the cork A and the air-tight piston c, there is a 

 closed chamber of air B. When the handle D, which moves the 

 piston c, is rapidly pushed in, it compresses the air until it is so 

 much condensed, that it forces out the cork A. 



Fig. 40. AIR PISTOL, OR " POP-GUN." 



855. Why must the handle le drawn out, before the corJc 

 is placed in ? 



Because otherwise a partial vacuum would be formed between A 

 and c, and there would not be sufficient air to force out the cork by 

 the return of the piston c D. 



856. Why does water rise in a syringe when the handle is 

 drawn out ? 



Because the pressure of the air on the water outside of the 

 syringe, forces it into the space vacated by the drawing up of 

 the handle, and where, otherwise, a vacuum would be formed. 



Fig 41. SYRINGE, WITH JET OP WATEB. 



857. Why does not the water run out when the syringe is 

 raised ? 



Because the pressure of the air upon the small orifice resists the 

 weight of the water. 



858. Why does the water leak out, lut not run ? 

 Because water has a tendency always iomove to the lowest point, 



