REPULSION AND ATTRACTION. 



expansion two or more gallons as it passes the 

 outer end, it follows that each part of it in the 

 expanded state must move more rapidly than 

 in the unexpanded state. So it comes to pass 

 that as it leaves the outer end of the small 

 hole, the steam has acquired a velocity of 

 several thousand feet per second. 



Light as steam is, when it moves with this 

 enormous velocity, it can exercise consider- 



FIQ. 24.-REPELLINQ AND ATTRACTING FORCE OF JETS. 



able force, as is shown in the driving of turbines 

 by such jets. 



The illustration (Fig. 24) shows another way 

 in which its power can be manifested. A is 

 a pipe communicating with a steam boiler. Its 

 upper end is blocked by metal pierced with the 

 fine hole B. The steam enters the lower end 

 of this fine hole at a speed of something like 

 1,400 feet per second, and as it passes along, 

 expands, leaving the upper end in a jet of 

 several thousand feet per second. When this 



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