188 AN EMPIRICAL STUDY OF GYRATING BODIES. 



It will be seen that this arrangement is in principle 

 exactly the same as the " gyrostatic balance" of Sir 

 William, but far more easily manipulated. Weights 

 can be attached to the hooks in the lower brass piece if 

 desired. 



In his paper, he says the "gyrostats 1 ' are all set 

 going at once in one direction, and then hung up by the 

 hook in the upper corner. I do the same with mine, save 

 that I place it with its point in the steel cup a, and lift 

 up the under piece, as in fig. 45. If there were no mo- 

 ment of momentum, the instrument should have no rota- 

 tion around a vertical axis. I take my hand from the 

 lower cross piece, and leave the instrument to itself. 

 Immediately it begins to rotate in the direction of the 

 arrow ellipse A (fig. 45). When the hand was taken 

 away abruptly, the lower end exhibited a slight oscilla- 

 tion for an instant or so, and then descended with no great 

 velocity, but quite uniformly as to rate, until the axes 

 were vertical, as in fig. 44. There was no pulling down 

 " to a distance proportional to the weight ; " in fact, the 

 only stoppage was at the end of its greatest possible fall. 

 With moderate skill in loosing hold of the lower piece 

 there was no oscillation whatever, at least none that 

 was large enough to be visible. 



The descent of the gyroscopes is not due to loss of 

 velocity from friction, for, by raising the lower cross- 

 piece, the process may be gone through several times 

 with once winding the wheels. The descent, even if 

 the rotational velocity were uniform, would still occur, 

 for the reasons pointed out when discussing the same 

 question for the simple gyroscope. 



Sir William appears to think that the effect of one 

 "gyrostat" neutralizes that of the other, or would do 

 so if all things were equal ; hence, he might say, per- 

 haps, that the rotation around the vertical axis was due 

 to the fact that, for some cause, some one of the "gyro- 



172 



