April 17, 19 13] 



NATURE 



77 



static control, operated in the manner just described, 

 is to endow the small ship with the period of a very 

 large one. 



In the second mode of operating the gyrostat , fric- 

 tion is introduced at the beariners on which the frame 



: tilted up to dt 



ichlick's method ofsteadyi 



of the gyrostat is mounted. With this addition the 

 ship is forcibly prevented from excessive rolling. In 

 the trials of the device it was found that with the 

 control in operation the angle of roll of the ship did 

 not exceed i° in a cross-sea which produced a total 

 swing of 35 when the control was out of action. It 

 is interesting to notice that, contrary to the opinions 

 which were expressed when the device was first sug- 

 gested, the preventing of the rolling of a ship does 

 not result in the waves breaking over her; a ship 

 controlled by a gyrostat is, I believe, a dry one. 



I have here a motor-gyrostat fitted within a skeleton 

 frame representing a ship (Fig. 12). The frame is 

 mounted on two bearings arranged on wooden up- 

 rights, and may be made to oscillate on these bearings, 

 so as to imitate the rolling of a ship in a cross-sea. 

 The frame of the gyrostat is mounted on two bearings 

 placed athwart the frame, and a weight is attached to 

 the outside of the case in a position in line with the 

 axis of the flywheel. The centre of gravity of the 

 gyrostat is in line with the bearings. A clip-device is 

 provided which allows the gyrostat to be clamped 

 to the skeleton frame, and provision is made whereby 

 a graded amount of friction may be applied at one of 

 the bearings. 



I now set the skeleton frame vibrating with the 

 flywheel at rest. You observe the period. I start the 

 motor-gyrostat, and repeat the vibrations, with the 

 gyrostat clipped to the frame. The ship rolls precisely 

 as before. I free the gyrostat from the frame, and 

 again set the ship rolling, when you see that not only 

 is the period vastly increased, but the rolling motion is 

 quickly wiped out. 



When the gyrostat is clipped to the frame it pro- 

 duces no effect upon the rolling motion. The coupler 

 opposing the rolling motion arise from the preces- 

 sional motion, and hence the gyrostat must be given 

 freedom to precess. In this connection it is interest- 

 ing to observe that in 1870 it was proposed by Sir 

 Henry Bessemer to obtain a steady cabin for a cross- 

 channel steamer bv placing- it on a gyrostat with its 

 axis vertical and supported on fore and aft trunnions. 

 This plan was bound to fail. The dependence of the 

 effect on freedom of the axis to precess in a direction 

 which is not that of rolling was not understood. We 

 now see that the object would have been attained by 

 supporting the cabin on fore-and-aft trunnions and 



NO. 2268, VOL. 91] 



mounting the gyrostat, within the cabin, on trunnions 



placed athwart the ship. 



Here is a monorail top of new design (Fig. 13). 



The frame on stilts represents the car, and mounted on 



pivots placed across the frame is a gyrostat. Carried 

 by a rod fixed to the frame of the 

 gyrostat, and in line with the axis 

 of the flywheel, is a weight. When 

 the frame is placed on the table so 

 that the legs and axis of the gyro- 

 stat are vertical, with the weight 

 above the flywheel, the arrangement 

 is doubly unstable without rotation ; 

 the system of gyrostat and weight is 

 usually mounted on the pivots, and 

 the entire structure is unstable about 

 the line oi contact of the feet with 

 the table. When the flywheel is 

 rotating, however, the top balances 

 on the table. The two non- 

 rotational instabilities have been 

 stabilised. 



I now place the top on the table 

 n ith the legs and axis of the fly- 

 wheel vertical, but with the weight 



g a ship in a cross sea. below the gyrostat. You observe 

 that the arrangement is unstable. 



Here there is only one instability without rotation, 



and the result is instability with or without rotation. 

 Here is a stilt top similar to the one just shown, 



but provided with wheels adapted to engage on a 



stretched wire. You observe the remarkable balancing 



power of the arrangement. 



13. — Xc 



irwil-tot . 



In this top (Fig. 15) a gyrostat is pivoted within a 

 structure which represents a tight-rope balancer. The 

 structure terminates in wheels adapted to engage on 

 the wire. Attached to the gyrostat are two arms, and 

 carried by these is a light rod weighted at both ends 



