246 Sir George Greenhill and Dr Bennett, Non-Spinning Gyrostat 



In the matter of his experimental illustration with the pen- 

 holder I was far from conjecturing that it was to be regarded as 

 ideally smooth; and if that indeed is to be the case it must be 

 further described as having precisely no angular velocity about its 

 axis, if it is to imitate the gyroscope successfully. 



It may be remarked that the suspension of a pendulous gyro- 

 scope by an altazimuth mounting is open to one grave objection: 

 that the gyroscope loses one of its three degrees of freedom in its 

 central position. And if the gyro-axis swings close past the vertical 

 it involves in consequence excessively rapid changes in the azimuth 

 movement of the suspension. The gunner who attempts to deal 

 with aircraft passing overhead, using the ordinary gun-mounting, 

 finds a corresponding difficulty with his training gear. Atw/cetl 

 7rai9 TToravov opviv. 



