380 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
board the Albatross was improvised by Ensign Henry B. Wilson, United States Kavy. 
The scales were marked with india ink on Irish linen writing paper, which was then 
glued to a wooden back, and finally given several coats of shellac varnish to protect 
it from moisture. Sewing silk was used for the arms, which were held in place by an 
ordinary elastic band fitting closely in the groove, and a small round nail was used 
for a pivot from which they worked. The left quadrant of the semicircle is used in 
the description and example; the right one may be used iu like manner by assuming 
that the ship’s head is in the direction of F instead of E. 
The instrument is used as though the vessel was always on the line C E, steering 
toward E, but in reality she was at G when the first bearing was taken and at H 
at the time of the second bearing, steering toward I on the line G H I, the pivot C being 
the point on which both bearings were taken. 
The distance-finder is constructed on the principle of Table 5 A, Bowditch 
Navigator. 
SUMNER’S METHOD. 
In the navigation of tlie Albatross, and the location of dredging, sounding, and 
other stations, Sumner’s method of finding the position at sea is used in extenso. All 
positions, however determined, are plotted as lines, and not points — the intersection 
of two such lines, corrected for the intervening run and current, defining the exact 
l^osition. The lines of position consist of i>ortions of circles of equal altitude of the 
sun, moon, stars, and planets; parallels of latitude deduced from meridian or ex 
meridian altitudes of the same bodies; lines of bearings of headlands or well-known 
objects on shore; circles of equal distance from known objects, found by micrometer or 
by their dipping below the horizon. Computations are made from forms and examples 
to be found in Bowditch’s Navigator. 
