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THE POPULAR SCIENCE MONTHLY 



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momentum, and the arrow T represents the torque which must act 

 upon the paddle-wheel shaft. To produce this torque the bearing a 



^ must push upwards on the crank 

 shaft, and the bearing b must push 

 downwards on the crank shaft, or 

 in other words, the crank shaft must 

 push downwards on bearing a and 

 upwards on bearing b, so that the 

 gyrostatic reaction of the paddle 

 wheels and crank shaft causes the 

 boat to list, sinking the side 00 of 

 the boat deeper into the water as it 

 turns round in the direction of the 

 curved arrow in Fig. 18. 



Fig. 19 is a side view of a 

 boat driven by a steam turbine and 

 propeller. The most serious gyro- 

 static action occurs in this case when 

 the boat is pitching violently in a 

 rough sea, and Fig. 19 is intended 

 to represent the bow of the boat as 

 rising as represented by the curved 

 dotted arrow. Under these condi- 

 tions the arrow 8 in the vector dia- 

 gram represents the spin-momentum 

 of the steam turbine and propeller 

 shaft at a given instant, 8' represents the spin-momentum at a later 



Fig. 18. 



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steam 

 turbine 



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Fig. 19. 



instant, AS represents the increment of spin-momentum, and the 



