120 REPORT ON 



The following are the designations and positions of the compasses which were 

 tised during the cruise : 



The Forward Alidade was a Sands Alidade Compass, and was on top of the 

 forward wooden pilot-house, 33.5 feet above the iron deck. 



The Forward Binnacle was a Ritchie Liquid Compass, and was in the binnacle 

 of the forward wooden pilot-house, 27.2 feet above the iron deck. 



The Forward Ritchie was a Ritchie Monitor Compass, and was 6.7 feet above 

 the top of the iron pilot-house on the forward turret. It was 22.1 feet above the 

 iron deck. 



Of these three compasses, the Forward Alidade and Forward Ritche were placed 

 exactly in the. vertical line passing through the centre of the forward turret, and 

 the Forward Binnacle was placed about two feet further forward, but nearly in the 

 same vertical plane. 



The Admiralty Standard Compass was on top of the after wooden pilot-house, 

 37.0 feet above the iron deck. 



The After Binnacle was a Ritchie Liquid Compass, and was in the binnacle of 

 the after wooden pilot-house, 27.2 feet above the iron deck. 



The After Ritchie was a Ritchie Monitor Compass, and was 6.7 feet above the 

 top of the iron pilot-house on the after turret. It was 2'2.1 feet above the iron 

 deck. 



Of these three compasses, the Admiralty Standard and After Ritchie were placed 

 exactly in the vertical line passing through the centre of the after turret, and the 

 After Binnacle was placed about two feet futher forward, but nearly in the same 

 vertical plane. 



The After Azimuth was a common Azimuth Compass which was set up temporarily 

 on the quarter deck every time the ship was swung ; small cavities having been cut 

 in the iron surface of the deck for the reception of the feet of the tripod, so as to 

 make sure that the instrument always occupied precisely the same position. It 

 stood 47.5 feet abaft the centre of the after turret, and there were two vertical iron 

 stanchions, each two inches in diameter, 10.3 feet high above the deck, and 12.1 

 feet distant from the compass, one of them being directly forward and the other 

 directly aft of it. This compass was elevated 4.6 feet above the iron deck ; but 

 when observations of magnetic force were made, it was necessary to remove it and 

 substitute an Admiralty Standard Compass, which occupied precisely the same 

 position, except that it was 4.8 feet above the deck. When the dip circle was 

 used it also stood 4.8 feet above the deck. 



It will be observed that all the compasses stood in the midships line, no matter 

 what their elevation above the deck might be. 



All the observations for determining the deviations of the compasses were made 

 by swinging the ship in the following manner : The true azimuth of a well defined 

 distant, object was determined by a solar bearing, as explained in Section III, page 

 26, and the declination of the magnetic needle having been applied to it, its true 

 magnetic azimuth became known ; then, supposing the sight vanes of the Admiralty 

 Standard Compass to be kept pointed steadily to that object while the ship was 

 swung, the reading which they would indicate on the azimuth circle attached to 



