[97] WOEK OF FISH COMMISSION STEAMER ALBATEOSS. 213 



for taking bearings and under the eye of the officer of the deck when 

 under way. 



In the month of April the local deviations were ascertained by azi- 

 muths of the sun taken on every point, the ship being upright and 

 swung by the helm under steam. One circle was made with starboard 

 helm and one with port helm, the mean of the results being accepted 

 as correct. The curve of deviations for compass courses was plotted 

 upon the Napier diagram, and a table of deviations for magnetic courses 

 was deduced for convenience in laying the ship^s head. In the accom- 

 l)anying steering card the points of the inner circle represent correct 

 magnetic courses, which are joined by radiating curved lines to the cor- 

 responding compass courses at the outer circle. 



Example. 



To malce a magnetic course east, steer by standard compass ESE. ^ E. 



The ship was also swung once while listed 4° to 6° to starboard and 

 once while listed 4° to 6° to port, azimuths being taken on every alter- 

 nate point. The greatest changes from tlie even-keel deviations were 

 on the NNE. and SSW. courses, the deviations on those courses when 

 listed to starboard being respectively 10° 11' W. and 17° 41' E., instead 

 of 3° 03' W. and 8° 20' E., as on an even keel. When listed to port the 

 deviations on these courses were 6° 10' W. and 12° 44' E., respectively, 

 instead of 3° 03' W. and 8° 20' E., as on an even keel. 



In general terms, it may be stated that the changes of deviations due 

 to inclination are such that when heeled to starboard the ship's head is 

 thrown to windward, or towards the higher side, when on any course 

 in the northern semicircle ; in the southern semicircle, when heeled to 

 starboard, the ship's head is thrown to leeward, or towards the lower 

 side. 



When heeled to port the ship's head is thrown to leeward when on 

 any course between southeast and northwest through north, and to 

 wiiidward when on any course to the southward of southeast and north- 

 west. 



At the same time that the ship was swung as above described, vibra- 

 tions of vertical and horizontal needles at the position of the standard 

 comi^ass were observed on the various courses by Lieutenants Kichard 

 Wainwright and S. W. B. Diehl, U. S. jST., on duty in the office of the 

 superintendent of compasses, Navy Department, to obtain the mean 

 values of A and //. The results of their observations will be published by 

 the Bureau of Navigation, Navy Department. 



This examination was made in latitude 38° N., off Point Lookout, at 

 the mouth of the Potomac Eiver, which ground affords every advantage 

 in point of space and smooth water. 



Lieutenants Wainwright and Diehl also made a magnetic survey of 

 the vessel in the month of June, while in the dry-dock of the navy-yard, 

 New York. 



