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REPORT ON 



reduce them to what they would have been if their lubber lines had not moved 

 For this purpose, whenever the ship was swung, a fixed line on the under side oi 

 the hurricane deck was produced till it touched the after turret, and then the 

 distance from its point of contact with the turret to a joint (marked number XII) 

 on the outside of the turret was measured. This distance, having been converted 

 into degrees and minutes by means of the known diameter of the turret, was the 

 correction to be applied to the position of the lubber lines. The following table gives 

 the measured distance, and its angular equivalent, at every station where the ship 

 was swung ; but it must be noticed that these corrections apply only to the After 

 Binnacle and After Ritchie Compasses. The lubber line of the Admiralty Standard 

 Compass was always properly adjusted before beginning to observe. 



When the ship was being swung, I always read the Admiralty Standard Compass 

 myself. Each of the other compasses was usually read by the officer whose name 

 is set opposite to it in the following table. 



Forward Alidade, 

 Forward Binnacle, 

 Forward Ritchie, 

 After Binnacle, 

 After Ritchie, 

 After Azimuth, 



Lieutenant M. Miller. 



Lieut. Miller, assisted by a Quartermaster. 



Lieutenant Geo. Smith. 



Ensign F. Wildes. 



Master Wm. Barrymore. 



Mate Jno. Ponte. 



My instruments for the measurement of magnetic force restricted me to the 

 method of deflections, and the only compasses on board at which that method 

 could be applied were the Admiralty Standard and the After Azimuth. As the 

 ship was always riding at anchor, and of course swinging a little, when such 

 observations were made, in order to render them as accurate as possible the follow- 

 ing plan was adopted. 



The deflecting bar was screwed to the movable circle which carried the sight 

 vanes of the Admiralty Standard Compass in such a position as to be at right 

 angles to them. That is, when the sight vanes pointed north and south the 

 deflecting bar pointed east and west. Then, 1. The sights being directed exactly 



