114 AN EMPIRICAL STUDY OF GYRATING BODIES. 



It will help us very much if we can get some certain 

 points in the wheel in which we can look steadily, see 

 how they behave ; then, extending our view, we may 

 take in all. We will endeavor also to get rid of all 

 extraneous matter. Therefore, let us suppose the ring 

 laid aside, since it serves only to hold the axle of the 

 wheel. Suppose, also, that the axle rests without fric- 

 tion directly on the top of the standard ; — the other part 

 of the axle being now useless may be regarded as cut 

 off ; — and we will confine our attention to a single section 

 of the wheel, making in fact a kind of tee-square, like 

 fig. 5. Its two extremities will be the two points desired. 



I would strongly advise every one who wishes to un- 

 derstand the gyroscope, to take in his hand a common 

 tee-square, and to do with it whatever is said to be done 

 in the following discussion. One that will answer every 

 purpose can easily be made by nailing a narrow strip of 

 wood, ten or twelve inches long, across the end of another 

 piece of about half the length. Then, for the sake of 

 convenient reference to direction of motion, let the experi- 

 menter stand facing the north with, of course, his right 

 hand to the east and his left to the west. This arrange- 

 ment I shall suppose to continue all through these 

 papers. Fig. 6 shows such a tee-square, one end sup- 

 ported on a standard, the leg horizontal and the arms 

 vertical. A p equals c p, so that A B subtends an arc of 

 90V 



The dotted lines, figs. 6 and 7, represent the tee-square 

 in its original position. 



If, now, the free end — fig. 6 — be allowed to fall ever so 

 little, the point A will acquire a motion towards the 

 right, and the point B a motion towards the left, repre- 

 sented by the arrows m and b. 



Suppose, at this moment, and while yet moving, the 



1 No such equality is really necessary, and it scarce ever occurs, but I adopt it now. A 

 more general discussion will follow soon. 



98 



