56 " MARION " EXPEDITION TO DAVIS STRAIT AND BAFFIN BAY 



the chart at the proper points along the track line. Both the bear- 

 ings and the depths were recorded against times read from the same 

 clock on the bridge, which simplified matters by making no correc- 

 tions necessary for time observed on different timepieces. 



The inshore soundings obtained are doubtless much more accu- 

 rately located in some instances than in others; for instance, the 

 soundings in the Arsuk Fiord region are undoubtedly much better 

 with regard to position than those taken in the fiord just south of 

 Aulalsivik Island, Labrador. For the latter place there was no large- 

 scale harbor chart, and it was noticeable that the fiord was actually 

 very different from tlie shape shown on the small-scale chart of 

 Labrador which had to be used. 



In view of the scarcity of recorded soundings on the charts of the 

 inland waters visited it is believed that the approximately located 

 soundings, such as those shown on Figures 44 and 45 of this pam- 

 phlet, will be useful until such times as the regions are carefully 

 surveyed and exactly located sounding values obtained and plotted. 



At sea whenever the echoes from the bottom could be heard 

 fathometer soundings were made at stations and also at least every 

 half hour while between stations. The location of these offshore 

 soundings was another matter from the location of the fiord and bay 

 soundings. The principles upon which the accuracy of the determi- 

 nations rest, however, are largely the same. The time as shoAvn by 

 the bridge clock and the sounding values observed were recorded in 

 a specially ruled notebook by the different watch officers, each one 

 taking and recording the soundings made during his watch. The 

 ship's positions offshore were determined by means of bearings of 

 prominent landmarks, when available, supplemented by nimierous 

 lines of ]30sitions obtained from sextant observations of heavenly 

 bodies. The latter position lines were the only available means of 

 locating the position when the ship was out of sight of land. 



The terrestrial bearings and the lines of position permitted the 

 ship's track to be drawn on the chart, and the Marion's successive 

 positions on this track, at intervals of 15 minutes, were carefully 

 indicated by short cross lines. The cross lines marking the hourly 

 positions were longer than those marking the half hour, while the 

 quarter-hour cross marks were the shortest of all. The date and 

 the ship's times from to 24 hours were written at the proper places 

 along the track, making reference at any time easy and certain. 



The soundings taken at sea were entered from the soundings book, 

 and recorded along the track on the plotting charts every two or 

 three days. The latitude and longitude of the soundings were also 

 entered to the nearest minute every two or three days in the sound- 

 ings book from the plotting sheets. Thus a double record of the 

 offshore soundings was maintained, which remains available for 

 ready reference to this day. 



The writer was in charge of the navigational work, so the accuracy 

 of the offshore soundings positions depends chiefly upon how many 

 properly worked-out sights he plotted daily. The longitude should, 

 in general, have been accurate, for there was a good chronometer 

 on board the 31 avion which was checked lip several times each week 

 by radio tmie signals from Arlington, Va. All the other officers 

 worked out sights occasionally, and these checked up consistently 

 with the plotted positions along the track line. 



