C. B. WARRING. 133 



On trial it will be found that the gyroscope will start 

 in its horizontal journey without these up-and-down 

 movements, if a little pains are taken to prevent its fall- 

 ing too rapidly at the start. This is easily accomplished, 

 after a little practice, by supporting the free end by a 

 string, and keeping the hand vertically over it. 



It will be found also that when the gyroscope is moving 

 with entire steadiness, these undulations can be pro- 

 duced at pleasure by pushing, or pulling, or striking the 

 free end. 



The following experiments show this very easily and 

 prettily : I set No. 2 (tig. 2) so that the wheel-end is 

 the heavier ; I made it twelve ounces heavier. Then I 

 attached to the hook, by a fine thread, a weight of six- 

 teen ounces — any other weight or proportion would do — 

 and set the wheel in motion and started it off. As I held 

 the end from falling too fast there was little or no undu- 

 lation. When it was gyrating with entire steadiness, I 

 flashed off with a match-blaze the attached weight. In- 

 stantly the gyration became very much slower and beau- 

 tiful undulations began. 



At another time with the weight, w, set as before, I 

 started the instrument, having first attached to the hook 

 a string ten or twelve inches long. As soon as the move- 

 ment was perfectly steady I pulled downward on the 

 string. Undulations at once set in proportional to the 

 degree of pull. By renewing the pull, I kept them up 

 indefinitely. If, however, the pull was steady and con- 

 tinuous, there were no undulations. 



These exioeriments prove that the undulations serve 

 no purj)ose in keeping the gyroscope up ; that they are 

 an accident not easily avoided save in skillful hands, 

 like the oscillations of a pair of balances ; and that 

 they are due to peculiar conditions of short continuance, 

 such as a blow, a momentary pull, or a sudden fall. 



117 



