1885.] NEW YORK ACADEMY OF SCIENCES. 37 



It falls SO very slowly, that this motion seems to be of no 

 consequence, but if it can't fall just as it pleases, it gets the 

 sulks, and falls as if dead ; in fact it won't stay up at all. The 

 horizontal motion also seems so small as if to be of no account, 

 but if it can't do that it won't do anything, and down it falls 

 at once. It is the most contrary piece of mechanism ev^er 

 invented. 



The two questions which most natm-ally arise when this in- 

 strument is exhibited are — first, why does it maintain the hori- 

 zontal position { and, secondly, why does it revolve around the 

 point of support i 



There are many other questions which any explanation must 

 meet and answer, but these are enough for the present purpose, 

 and answering them really answers all. 



Those who are familiar with the literatm-e of the subject are 

 aware that many attempts have been made to show why the 

 Gyroscope acts in this manner. Some of the explanations are 

 absurd, while others bring in the higher mathematics, and 

 therefore can be understood l)y but few. 



Some attribute the two effects largely to friction, Init this ex- 

 planation is disproved by the simple fact that the less the fric- 

 tion the better the instrinuent works. A writer in Appleton's 

 Encyclopedia says that gravity acts with the motion of the 

 disk on one side and against it on the other ; i. e., the side which 

 is going do^vnward is accelerated by gravity, while the other 

 side, moving upw^ard, is retarded. Thus there is a greater force 

 on one side than on the other, and, of course, the Gyroscope is 

 pushed around by the greater force. This is sufficiently dis- 

 proved by placing the instrument so that it is free to move 

 around its support horizontally, but not to fall any. It is found 

 on trial that no matter how fast, or how slow, the disk revolves 

 on its axis, there is no horizontal motion whatever. Without 

 going any fm-ther in the explanations which have been offered, 

 it is enough to say that the problems involved have been re- 

 garded as offering very considerable difficulty, and in all school 

 works are passed over without any real solution. 



The two questions which have been mentioned I shall en- 

 deavor to answer. 



1st. Why, in apparent defiance of the law of gravitation, 

 does the Gyroscope, when supported only at one end, remain in 

 a horizontal position ? 



