296 THE SPERRY GYRO-COMPASSiIN SERVICE. 



in service, not only in placing the compass on the meridian by hand when it 

 is first started, but also for checking the compass at any time. A glance at 

 the level on the sensitive element will tell the observer instantly as to whether 

 the compass is on the meridian as even the slightest deviation of the compass 

 will change the position of the bubble. The petty ofiicer charged with the 

 care of the compass on the U. S. S. North Dakota was very em.phatic in 

 stating that he didn't need to be told from aloft when the compass was on the 

 meridian by observations of the sun; he already knew it by the position of 

 the bubble in the compass level. 



On the submarines having a gyro-compass it was found to be of the 

 greatest value not only in navigating but in making an attack. By taking 

 an observation of the ship to be attacked when seven or eight miles distant, 

 the submarine can be run completely submerged and steered so accurately 

 that it is possible to obtain exactly the right position for discharging tor- 

 pedoes before rising to the surface for the final sight. 



The title of this paper might convey some idea to the effect that the 

 intention is to describe the methods of operation of the compass and experi- 

 ences in its upkeep and adjustment. If the paper should treat of that alone 

 its presentation would be hardly warranted because the operation and main- 

 tenance of the instrument is so very simple. 



The installation of the instrument involves nothing complicated inas- 

 much as the only adjustment necessary is to properly place the lubber's point 

 so that the true angular position of the ship's head is always shown. 



In wiring and connecting up the instruments and switchboards, the 

 usual navy standard wiring practice is always followed. 



The starting of the instruments is merely a question of properly manipu- 

 lating the facilities provided for accelerating the motor-generator. This 

 occupies a time of approximately fifteen minutes. 



The adjustment of the meridian by means of the levels has already been 

 described. The only other adjustments necessary in handling the instru- 

 ments are the adjustment for speed and latitude, made on the small dials 

 provided for that purpose, and the adjustment of the head of the suspension 

 wire, which is made by means of a tangential screw on this head, the object 

 being to bring the sensitive element exactly i n the center of its surrounding 

 frame, or phantom ring, when the wheel is not spinning and the sensitive 

 element is hanging as an inert mass. 



A small pointer, placed on the trolley posts referred to above, exactly 

 coincides with the black line on the block carrying the silver contracts when 

 the suspension wire is in perfect adjustment. 



