MARION 



EXPEDITIOiSr TO DAVIS STRAIT AND BAFFIN BAY 



55 



Two things are necessary to make a sounding of value for use on a 

 chart: First, the geographical position where it was taken must be 

 known quite accurately ; second, the sounding must be nearly correct. 

 The Marion soundings can be divided into two groups, a less impor- 

 tant one comprising those taken in harbors and sheltered waters, and 

 a more important one comprising those taken in the open sea. In 

 neither of these groups is the determination position all that could be 

 desired. The unfamiliarity of the personnel with the unlighted and 

 practicall}^ unmarked coasts and harbors made accurate determina- 

 tion of the position of soundings taken inshore most difficult, espe- 



TlIE CONTROL I'AXEL OF THE FATHOMETER 



Figure 41. — This box, usually installed on the bridge, is used 

 to start and stop the fathometer and to control the fre- 

 quency and intensity of the signals. There are two scales 

 on its face, one graduated from to 100 fathoms and the 

 other from to 600 fathoms. The latter is for use in deep 

 water. Tlie amplitied echoes permit the depth of water to 

 be instantly obtained from one or the other of the above- 

 mentioned scales. (Courtesy of the Submarine Signal Co.). 



cially in view of the fact tliat the places were but once visited in every 

 case, and then always for a very short time. 



The soundings taken while cruising in bays and fiords were re- 

 corded against times in a book by an officer stationed at the fath- 

 ometer. Another officer cut in the ship's position at frequent inter- 

 vals on the chart being used. This was accomplished by means of 

 laying down observed magnetic compa.'^s bearings of identified points 

 and islands from time to time. The bearing observer, by means of 

 the plotted bearing lines on the chart, could determine the approxi- 

 mate track of the ship, and, gTiided the times of the recorded depth 

 values in the soundings book, could later place the soundings on 



