Chapter II 

 THE BATHYMETRY 



INTRODUCTION 



Detailed knowledge concerning the depth of ocean basins and 

 other large bodies of water is valuable to two classes of peoj^le: 

 Those concerned with the navigation of ships and those who, like 

 the geologist and geographer, desire to learn more facts about the 

 earth. There is little sea-borne commerce in the Davis Strait area, 

 so the bathymetrical information contained in this bulletin will 

 prove of but slight practical value to most mariners of to-day, though 

 new discoveries and new northern developments in the future may 

 cause it to be of more value to them at some later date. On the 

 other hand the detailed depth values discussed here should prove 

 of considerable interest to geological and geographical workers, 

 especially to those connected wdth the field of oceanography. 



Dozens of expeditions of discovery and rescue have traversed the 

 Davis Strait area, and a varying number of commercial vessels have 

 frequented it annually for centuries. It is astonishing, in view of 

 this, how few in number are the sounding values which appear on 

 the charts, and what great areas exist between Labrador and Green- 

 land in which, apparently, prior to the year 1928, no sounding was 

 ever taken. Before the development of sonic depth-finding methods 

 a great expenditure of time and trouble was necessary to obtain good 

 soundings in deep w^ater. This fact probably explains the lack of 

 detailed bathymetrical knowledge of the Davis Strait area which 

 existed prior to the time of the Marion Expedition. 



DESCRIPTION or APPARATUS AND METHODS 



The Marion was equipped Avith a commercial echo sounding device 

 of the same type as those used on the international ice-patrol vessels 

 since the beginning of 1928, It was manufactured by the Submarine 

 Signal Corporation, of Boston, Mass., and w^as called a " fathometer." 

 (See figs. 40 and 41.) This instrument was capable of instantly 

 showing the depth of water up to nearh^ 100 fathoms by the flashing 

 of a red light opposite the proper depth value on a circular scale 

 marked in fathoms. It was possible to make an easy adjustment 

 which would slow down the apparatus to one-sixth speed. This ad- 

 justment automatically cut out the red light and threw in a steady 

 white light on the disk moving past the depth scale. After this was 

 accomplished with the aid of ear phones to detect the echoes returning 

 from the sea bottom, the ap])aratus could be used to measure the 

 depth of water up to a maximum, under favorable conditions, of 

 over 2,000 fathoms. 



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