MECHANICAL PARADOXES. 



The tube B is supposed to be too small for 

 water to run down and air to run up at the 

 same time say, a quarter of an inch diameter. 

 Now, the pressure of the air being nearly 

 fifteen pounds to the square inch, its pressure 

 upwards against the water in the lower end 

 of such a tube would be about three-quarters 

 of a pound. But a column of water of that 

 size would have to be 34 feet high in order 

 to weigh three-quarters of a pound. It is 

 clear, therefore, that if a tube of that length 

 were filled with water and its upper end were 

 closed, the atmospheric pressure would hold 

 up the water inside it. The same pressure 

 would have no difficulty in holding up the 

 water in tubes of a few feet or inches, such 

 as are commonly used for experiments. 



If a tube of this size were bent in something 

 like the shape shown at D, and its lower ends 

 were both open, the atmospheric pressure 

 pressing anything into the one end would 

 balance the same pressure at the other. If 

 the whole tube were full of water, and the 

 whole height of the one leg from the top of 

 the bend to the lower opening were exactly 

 equal to the height of the other that is, if their 

 lower openings were on a level the water- 

 pressures also in the two legs would exactly 

 balance, and the tube would remain full with 

 both ends open. 



Practically it would be as impossible to 



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