C. B. WARRING. 157 



Eationale : Friction prevents the foot-piece from re- 

 volving horizontally. Hence when the top molecule, m, 

 tilts towards the observer, and moves towards p, it can- 

 not push the opposite molecule, q, away from him, and 

 consequently q will, when it arrives at the top, be desti- 

 tute of any tendency to push that portion away from 

 him, or, in other words, it will have no power to push 

 the instrument back to its place. 



THE GYROSTAT ON STILTS AND ON WHEELS. 



Fig. 33^, plate II, shows another form of gyrostat. It 

 explains itself, except, perhaps, that I should say that 

 the little wheel is placed so that its axis is approximate- 

 ly in the plane of the large w T heel, and that its frame is 

 connected at a, rigidly with the frame of the gyroscope. 

 The point d may either rest in a loose socket, or may 

 be free upon the surface of the glass plate x y. 



Set the wheel in motion, and let it slightly lean to- 

 wards the observer ; the whole system will begin to re- 

 volve around d in the direction of the arrow m. Let it 

 lean the other way ; at once the little wheel will begin 

 to go backward. In either case, the leaning will slowly 

 increase (velocity m also increasing at the same time), un- 

 til at last the instrument falls. That the fall is not in- 

 duced by the loss of velocity on the part of the gyroscope 

 wheel from friction, is evident, because the machine may 

 be set up and made to go through the process several 

 times with one winding of the wdieel ; and, furthermore, 

 the fall will be very greatly accelerated by friction at the 

 axle of the little wheel, or by obstructions in its w T ay. 



If, in any case, when the instrument is falling, e. g., 

 towards the observer, pressure be applied at o, in the 

 same direction, it will become vertical again. 



Rationale : That of the horizontal motion is the same 

 as in the previous experiments. The rationale of the 

 rise to a vertical is in principle the same, but somewhat 



141 



