ACTIVE TYPE OF STABILIZING GYRO. 207 



This stabilization of ships has been undertaken by two methods : — First, 

 by changing the center of gravity of the mass as a whole, as by the damping 

 tanks of Sir Philip Watts and later workers, and the moving weights already 

 successfully applied by Sir John; and second, by employing the already very 

 great longitudinal stability or rigidity by deflecting same in to the athwart- 

 ship plane. The ship by this means may be rendered stable almost without 

 limit and up to the breaking-down point of the gyroscopic couple, which has 

 now come to be recognized as of simple origin and of very great magnitude, 

 especially as compared with the weights involved. 



Some of the early attempts to use the gyroscope were unfortunate in 

 that the gyro was passive, therefore free and uncontrolled as to its precessional 

 movements. Experience has now been had in actual sea trials which confirm 

 statements often put forward by the author, urging the great importance 

 of having these precessional movements of the gyro at all times under 

 perfect control. This arrangement introduces into the art a number of very 

 important advantages which are now of definite and proven worth. This 

 control on the one hand sets a constant limit to the otherwise almost limitless 

 power of the gyro couple, while on the other hand it allows us to apply a 

 measured stress of any desired magnitude, duration or direction and that 

 may be timed with precession. In this manner, the very great longitudinal 

 metacentric height is available for athwartship purposes and may be in any 

 desired amount added to the athwartship component. In fact the point has 

 now been reached in this development, as demonstrated by sea trials, that 

 the amount of the great longitudinal stability utilized athwartship may be 

 always quantitative and proportional to the needs. With this auxiliary fitted 

 the ship itself may be very tender and of low metacentric height because, as 

 above stated, any desired amount of the very great longitudinal metacentric 

 height may be added at will athwartship, and this without any regard to the 

 rolling period of the ship. In this manner a comparatively small apparatus 

 can be utilized in effectually holding the ship against motion, simply because 

 each increment on the instant, and simultaneously with its development, is 

 completely neutralized before it has time to move the ship. 



The gyro constitutes an ideal apparatus for this work inasmuch as it is 

 perfectly safe. It is unnecessary to run the wheel at any but comparatively 

 low stresses. In fact, the stresses present can be brought below those used 

 in hull practice. The comparatively slow motion of the wheel is very inex- 

 pensive to develop and maintain, representing only a small fraction of the 

 power required to propel bilge keels; and this power, small as it is, is only 

 required when the necessity for stabilizing arises and then only in proportion 

 to the seas running at the time, whereas the power for the bilge keels is omni- 



