148 THE GYROSCOPE FOR MARINE PURPOSES. 



mass can be made to do a very large amount of work, owing to the velocity 

 that may, at low cost, be impressed upon it. One instance has been noted 

 where the power required for operating the gyroscope would be about five per 

 cent of that required for driving the bilge keels at normal speed of the boat, 

 the keels requiring power in all weathers, the gyroscope only when needed. 

 A primary motion on the part of a body, for instance, the slow athwart- 

 ship or rolling motion of a ship, exerts gyroscopic forces upon any vertical 

 spinning shaft and in a fore-and-aft direction. These forces tend to dampen 

 the rolling motion, but only feebly, and the fore-and-aft reaction, owing 

 to the absence, of motion, does not at all. It is a part of the general plan 

 to so utilize this force as to make it create extremely large reactions athwart- 

 ships or in the proper direction to be effective. This is accomplished by 

 the ingenious yet simple expedient of mounting the aforesaid vertical shaft 

 in a pivoted frame so that it can tilt and utilize the primary fore-and-aft 

 reaction to cause the axis of the spinning mass to tilt fore and aft. This 

 motion is of much higher velocity than the angular motion of the vessel 

 which produces it. By means of this tilting motion an entirely new gyro- 

 scopic force is set up again at right angles as in the first instance, but now 

 to the plane of tilt (fore-and-aft) which brings it back to the original 

 athwartship plane just where needed; and, what is equally important, the 

 reaction is in a direction exactly opposed to the roll of the ship which 

 primarily called it into action, as well as this whole chain of phenomena 

 which we have thus traced through a complete cycle of 1 80 degrees of angle 

 and also through an enormous augmentation of righting moment and 

 stabilizing power. 



In Plate 53 we have a pendulum with a small gyroscope mounted upon 

 it. This pendulum has freedom of oscillation upon its two gudgeons, all 

 ship's roll being pendulic; this may be considered to be a ship with a small 

 gyroscope upon it. The spinner weighs but little and it spins at a very 

 low velocity compared with what a well-organized gyroscope will do. 



THE ACTIVE GYROSCOPE. 



We note in Plate 54 that a cord is seen passing through the two gud- 

 geons of the pendulum just above the tripods, and at a point midway 

 between these gudgeons the cord passes around one of the little horizontal 

 pulleys immediately below the gyroscope arranged in an elongated opening 

 in the wooden top of the pendulum. These pulleys operate the little 

 pinions in the lower middle portion'of the fork of tlie gyroscope, one being 

 geared directly to the base ring, shown horizontally in Plate 54, and the 



