SOLIDS DEFYING GRAVITY. 



and B a circular frame in which the ends of 

 the axle are supported on pivots in screw-knobs 

 which admit of adjusting the tightness of the 

 bearings. It can be spun by a string passed 

 through a hole near one end of the axle, and 

 wound round the axle. 



Hold the gyroscope, while spinning briskly 

 in a vertical position, by the two knobs, which 

 are therefore level. Try to tilt the instrument 

 by raising one knob, C, and depressing the other, 

 D. The spinning wheel will offer a great re- 

 sistance to this twist, and very likely will 

 twist itself in another way, with a most uncanny 

 appearance of perversity, out of the grasp of 

 one who is experimenting with it for the first 

 time. It behaves almost as if it were alive, 

 and offers what seems like an intentional resist- 

 ance to twisting. It can be lifted and lowered 

 quite easily, for its weight remains unaltered ; 

 it may be moved from side to side or back- 

 wards and forwards just like any inert body, 

 provided that its plane of rotation, and there- 

 fore its axis of rotation, be kept looking in the 

 same direction. But any attempt to make it 

 face another way round is stoutly resisted, and 

 in the struggle it often twists itself out of the 

 experimenter's grasp. The larger and heavier the 

 gyroscope, and the more vigorous its spin, the 

 more powerful is the resistance that it makes. 



Now when the gyroscope is spinning with 

 a vertical plane of rotation, and therefore a 



27 



