/c 





UJI LIB i^ A R y |<^, 

 OCEANOGRAPHY \^\ ,^_ /r^/ 



1. Sounding work. 



2. Station work. 



3. Isotherms as current indicators. 



4. Miscellaneous. 



1. SOUNDING WORK 



Echo soundings were taken during the 1930 ice season at frequent 

 intervals by the ice-patrol vessels while en route to and from patrol 

 as well as while in the ice regions. Commercial depth-finding instru- 

 ments of the type carried during the past two years were used. 



Considerable trouble was experienced with the sound-amplifying 

 devices, but it was possible to keep the whole apparatus in operating 

 condition about 90 per cent of the time. 



When in good order, the machines could usually measure depths of 

 less than 1,000 fathoms. Depths between 1,000 and 2,000 fathoms 

 could frequently be measured when the water noises from waves and 

 from eddy disturbances about the hull were not too great. Depths 

 ^ver 2,000 fathoms could sometimes be measured when conditions 

 were especially quiet and favorable. 



All depth values taken when the ship's geographical position was 

 in doubt, though valuable for immediate navigational purposes, were 

 discarded so far as permanent records are concerned. Several hun- 

 dred values taken when the position was well known, both as to lati- 

 tude and longitude from recent and reliable observations, were cor- 

 rected for the salinity, temperature, and pressure of the water column, 

 and transmitted to the United States Hydrographic Office and to 

 the Coast and Geodetic Survey. 



Some depth observations were furnished to the Geophysical 

 Laboratory, Carnegie Institution of Washington, which organization 

 was particularly interested in the ice patrol's soundings for 1930 

 because of the earthquake of November 18, 1929, during which 

 certain areas just west of the Grand Banks were thought by some 

 scientists to have foundered. Whenever the patrol's tests were made 

 near the positions of former soundings on the charts, the results 

 showed about the same depth of water as before the earthquake. No 

 evidence was gathered substantiating any widespread foundering. 



In a number of instances the fathometer readings were checked by 

 carefully taken wire soundings. In every such case the depth values 

 obtained by the two methods were in close agreement. 



The patrol operates most of the time where many soundings have 

 been taken, but occasionally regions with very few charted depth 



(35) 



