73 



The bottled water is next siphoned into the test cells of tlie electric 

 salinometer, an instrument which conveniently measures the total 

 solid salts of the sample per thousand grams of water. (See C. G. 

 Bull. No. 12, pp. 136-147; and Bull. No. 15. p. 125.) There were 

 over 1,000 samples of sea water tested for salinity by this instrument 

 during the patrol of 1927. The next step is to convert temperature 

 and salinity values into terms of specific gravity, and from these 

 latter the currents are calculated. The final result of the current 

 surveys are such sketches and maps as Figures 33 to 52. Such cur- 

 rent maps, moreover, have proved of great value to those in direct 

 charge of the patrol, as they reveal information on the probable 

 movements of the ice. 



The installation in 1927 of new electric oceanographic winches 

 to lower and hoist the instruments materially shortened the time 

 spent at stations, and thus allowed a greater number to be taken. 

 A total of 208 stations, nearly double the number of any previous 

 season, were located around the Atlantic faces of the Grand Bank. 



The surveys were made in the following order: The first part of 

 April the so-called critical area around the Tail of the Bank was 

 surveyed. Two weeks later observations were repeated in the same 

 region to determine what changes, if any, had taken place. The 

 first part of May the Modoc investigated the water mass lying along 

 the east side of the Bank from the forty-sixth parallel southward 

 around the Tail and for a distance of 150 miles to the westward 

 along the southwest slope. Three weeks later the currents were 

 traced along the east side of the Bank by the Tampa for a distance 

 of 120 miles north and south of a point on the slope where the warm 

 offshore water pressed in. The final investigation for 1927 was 

 conducted by the Modoc the second two weeks in June, and embraced 

 the entire eastern slope of the Grand Bank from its northern reaches 

 to the Tail and eastward to Flemish Cap. This was the most exten- 

 sive survey ever conducted by an ice patrol vessel, and presented 

 to those in charge of the work a most detailed picture of the ice and 

 current conditions near the close of June. It was upon the informa- 

 tion contained on the current map for this period that the strong 

 recommendation to discontinue the patrol June 25 was based. 



DISCUSSION OF THE CIRCULATION IN 1927 



The total of 208 stations has, for the purposes of illustration and 

 discussion, been divided into five groups or sets, arranged chrono- 

 logically for the periods observed. Each set contains four maps — one 

 dynamic topographic of the sea surface, one showing the direction 

 and velocity of the currents as calculated, one representing the 

 distribution of the cold and warm water, and one showing the relative 

 positions of the fresher and Salter masses. 



