636 Professor Andrew Gray [Feb. 14, 



coincident with that of the torpedo — that is pointed, so to speak, 

 exactly along the " cigar." Any turning of the torpedo body side- 

 ways brings about a relative shift between the gyrostat and torpedo 

 axes, and this shift Inings into operation a vertical rudder at the stern 

 of the torpedo. If the nose of the torpedo turns to port, the rudder 

 steers the craft to starboard, and vice versa. 



Here (Fig. 2) is a skeleton frame representing a torpedo. It is 

 mounted on a vertical axle, and carried on pivots within the struc- 

 ture is one of our motor-gyrostats. At the stern of the frame is a 

 small rudder, and this is connected by means of cords to the gyro- 

 stat. I set the flywheel in rotation. When, as I do now, I turn the 

 nose of the torpedo to port, the rudder steers to starboard ; when I 

 turn the nose to starboard the rudder steers the craft to port. 



The case of the pedestal gyrostat is provided with a hook at one 

 extremity of the axis (see Fig. ?>). The effect of hanging a weight 

 on this hook is to apply a couple tending to cause turning about the 

 axis (2) — that is, which would produce such turning if the fly-wheel 

 were not spinning. But the wheel is spinning, and the visible actual 

 turning is about the axis (3). Observe also that the wheel is rotating 

 comparatively slowly, and that the precessional motion is great. 

 I increase the speed of the fly-wheel and the gyrostat precesses more 

 slowly. I replace the weight by a larger one, and for the same spin 

 the precessional motion is greatly increased. Thus for a given 

 applied couple the faster the spin the slower the precessional motion, 

 and for a given spin the greater the couple the faster the precessional 

 motion. 



Now while the weight is in position and the gyrostat precessing 

 about the axle (3), I attempt to hurry the precessional motion, and 

 immediately the gyrostat turns about the axis (2) so as to rise against 

 gravity. I try to delay the precession, and again the gyrostat turns 

 about the axis (2), but now so as to descend under gravity. 



Without being aware of it, people are constantly meeting with 

 examples of gyrostatic action in daily life. A child expert in trund- 

 ling a hoop causes it to turn its path to the right or left, by striking 

 it a blow at the top with the hoop-stick, the effect of which the 

 ordinary person would suppose, if he thought about it, should be to 

 make the hoop to fall over to the right or the left. A bicyclist riding 

 without holding the handles leans over to the right if he wants to steer 

 the bicycle to the right, and to the left if he wants to steer to the 

 left. And if he feels himself falling over to right or left he turns 

 the handles instinctively so as to turn the bicycle to that side, when 

 the machine resumes the upright position. In the bicycle, however, 

 the spin of the wheels is not the most important action to be taken 

 account of. 



The gyrostatic action in the bicycle is much more marked in a 

 motor machine, for in that a massive fly-wheel rotates in the same 



