WORKING WONDERS WITH A TOP 



oscillating masses of unmanageable size. The princi- 

 ple on which the Sperry ship-steadying gyroscope 

 works is that of anticipating the rolling motion of the 

 ship, and, so to say, nipping it in the bud. The 

 Schlick gyroscope could not get into action until a 

 precessional stress had been brought to bear on its 

 axis by the actual rolling of the ship. But Mr. Sperry 

 conceived the idea of giving a precessional thrust to 

 the axis of the gyro with the aid of a steam engine ; 

 such thrust being timed by the action of a very small 

 gyroscope which would feel the slightest departure 

 from the level. 



The large active gyro is arranged with a horizontal 

 axis lying athwart the ship. The so-called preces- 

 sional engine is so arranged that when it operates it 

 gives a horizontal thrust to the end of the gyro- 

 scope's axis lengthwise of the ship. Such a thrust 

 obviously causes the axis of the gyroscope to attempt 

 to precess in a vertical direction, thus straining at 

 its bearings rigidly bolted to the ship's steel frame- 

 work in such a way as to resist the tendency of the 

 ship to roll. There is no marked oscillation of the 

 mass as in the Schlick gyroscope, and as the preces- 

 sional engine is brought into action almost in antici- 

 pation of the motion of the ship, a relatively small 

 expenditure of power suffices to hold the ship on an 

 even keel. 



A curious additional possibility with the Sperry 

 gyroscope is that, with the aid of the precessional 

 engine, the apparatus may be made to bring such a 

 strain on the ship as to cause it to roll in perfectly 

 smooth water. This was demonstrated on the U. S. 



269 



