72 eepor't of commissioner of fish and fisheries. [70] 



found ill higher latitudes, though of course less marked. When listed 

 to starboard the ship's head is thrown to windward when ou courses 

 north of east and west, and to leeward when on courses south of east 

 and west. When listed to port the ship's head is thrown to windward 

 when ou any course west of north and south, and to leeward on any 

 course east of north and south. The greatest difference caused by 

 starboard list was on a southwest course, when the deviation was 11° 

 15' E. as compared with S° 30' E. on even beam. The greatest change 

 caused by port list was on a northwest course, when the deviation was 

 5° 15' B. as compared with 2° 30' E. on even beam. 



In the month of July a magnetic survey of the vessel was made while 

 in the dry dock of the navy-yard, Norfolk, Va., and the data sent to the 

 Navy ])epartmeut. 



The geueral methods of navigation were as described in the report 

 for 1883. The following examples will serve to illustrate the practical 

 working of them : 



Example I. — On January 15 the problem was to sound over the posi- 

 tion of Mourand Shoal, latitude L'lo 35' N., longitude G5o 13' W. An 

 altitude of the sun taken at 8.20 a. m., and worked out for latitudes 25° 

 and 25° 10' showed the ship to be somewhere ou the line A B (Plate II). 

 Clouds interfered with subsequent time-sights, but it was seen that if 12 

 miles were made on the same course (IS. by E. ^ E.) the ship would be on 

 a line passing over Mouraud Shoal and parallel to the line of jiosition 

 found at 8.20. So, when that distance had been made, it being believed 

 that the ship was to the northeastward of the shoal, the course was 

 changed to run southward along that line, and, as the hour of noon 

 approached, ex««ieri(lian altitudes were observed and comi)uted in quick 

 succession. Finally, a short time before noon, the latitude of 24° 35' 

 was reached. The ship was immediately stopped and the sounding 

 begun, Xo. 39. The meridian altitude taken while sounding gave 24° 

 35' 14" as the latitude; and as no current was detected while sounding 

 (3,006 fathoms), the vessel wa.s presumably in the required longitude 

 also. 



Example II. — During the night of April 11 and 12, while sounding 

 at 8.15 p. m., altitudes of Sirius and Capella were taken and worked out 

 for latitudes 18° and 18° 10', placing the ship at Station No. 401, the 

 intersection of the two lines of equal altitude. It was found necessary 

 to steam ahead about 2 J knots an hour E. hy S. to keep the wire verti- 

 cal. The couive was then shaped for the vigia, making allowance for 

 the westerly current, and a sounding taken about midway. The cur- 

 rent was here found to have changed to the eastward, quite feeble, and 

 altitudes of Vega and Polaris showed the ship at No. 402. The difier- 

 euce between the intended and actual positions corroborated fairly the 

 change of current. The course was then shaped for the vigia again, 

 and a sounding taken a few miles southward of it so as to have a defi- 

 nite starting point not far from the desired position. The current was 

 here found to be setting to the W^SW. about 2 knots, and altitudes of 



