294 THE SPERRY GYRO-COMPASS IN SERVICE. 



which happened while coming into the harbor of New York which serves to 

 illustrate one of the many advantages of the gyro-compass. This officer 

 happened to be on the bridge when the ship was off Block Island and steaming 

 toward the entrance to New York Harbor. The captain was on the bridge 

 and conning the ship. Upon laying out the next change of course he found 

 that it would be "6 true;" so he merely said to the officer of the deck "6 by 

 gyro, " and the officer of the deck gave the course to the helmsman, no calcu- 

 lation being necessary, as the helmsman had before him a repeater compass. 



Suppose the captain had wished to change the course, using the old 

 magnetic compass. If the compass rose of the chart had been marked rela- 

 tive to true north it would have been necessary for the navigating officer to 

 have first applied the variation at that latitude, having corrected the varia- 

 tion for the elapsed time since the chart was printed, then apply this variation 

 to the true course to obtain the magnetic course, and, with this magnetic 

 course as an argument, look in the deviation tables for the deviation of the 

 compass at that heading. This deviation would be marked "East" or 

 "West," and in applying it to the magnetic compass to obtain the course by 

 standard compass the navigator would have to think carefully as to which 

 way it should be applied, imagining himself at the center of the compass card, 

 applying westerly deviation to the right and easterly deviation to the left to 

 obtain the compass course. Having obtained the course by standard com- 

 pass, it would be necessary for the officer of the deck to climb to the standard 

 compass, which on ships of the Florida type is located in the mast, about 

 fifteen feet above the steering platform, and with his eyes on the standard 

 compass he would have had to conn the helmsman to the proper course by 

 standard compass, checking the course several times to be sure that no error 

 was introduced by lag. Having found from the standard compass what the 

 course should be by the steering compass, the officer of the deck would 

 descend from the standard compass and report the ship on her course. 



This is only one of the many valuable points brought out in practice. 

 Perhaps the most valuable from the point of view of a naval officer are those 

 which have to do with tactics. The pelorus dial can be made a repeater 

 compass so that on line of bearing it is not necessary to call back and forth 

 between the compass and the pelorus when getting the bearing of the flag- 

 ship. Turning the vanes of the pelorus on the flagship and glancing at the 

 card of the pelorus shows us immediately the true line of bearing. This 

 feature is also of great value in taking bearings when navigating by land falls. 



Many fleet formations in present-day tactics are on line of bearings and 

 in maneuvering a fleet it is frequently necessary to change from one line of 

 bearing to another. In using the magnetic compass for setting the pelorus, 



