102 AN EMPIRICAL STUDY OF GYRATING BODIES. 



ciety, 1854, describes and gives a diagram of a gyro- 

 scope much like this. The conical support of my instru- 

 ment with the polished steel cup in which it rests is 

 greatly superior to his arrangement, since it much more 

 nearly eliminates what may be called the horizontal 

 friction. 



10. If while balanced on its line point, the weight be- 

 ing placed so that the arm is horizontal, and the wheel 

 being at rest, the instrument is made to revolve rapidly 

 on the standard, it will continue in motion, until, after 

 some minutes, the friction and resistance of the air bring 

 it to rest. Evidently it possesses momentum, and, if 

 brought against an obstacle, would strike it a hard blow. 

 Now set the wheel in rapid motion, and attach a weight 

 to the free end by a thread a few inches long. It will 

 at once begin to revolve around the fixed point at a rate 

 proportional to the weight attached. When in full mo- 

 tion cut the thread with a match blaze. The gyration 

 will cease the instant the weight drops, as abruptly as if 

 the gyroscope had run against an obstacle, or as if it 

 had no momentum. 



This is one of the new and singular effects of which 

 I spoke a little while ago. 



To make this succeed most perfectly a few precautions 

 are necessary : After the instrument is balanced, the 

 wheel in operation, and the weight attached, raise the 

 gyroscope so that the axis is 10° or 15° above a hor- 

 izontal. Then let it go. Watch it as it slowly descends 

 and flash the thread (or cut it with sharp scissors) just 

 as the axis becomes horizontal. The stoppage of 

 forward movement will then be perfect. 



11. If the ring is taken in the hand while the wheel is 

 in rapid motion, and an effort made to turn the instru- 

 ment in various directions, it will resist with surprising- 

 force. 



Perhaps nothing in the whole series of experiments, 



86 



