73 



flow and would be misleading instead of useful, in view of the bulb and 

 eddy circulation that actually exists. 



Even though scant opportunity was afforded for making station 

 networks, a good many single stations were taken for information and 

 practice, as just before the start of a day's scouting, just after dark 

 when stopping for the night, bj^ a newly found berg, or when stopped 

 by dense fog. These isolated observations gave information about 

 the lower water levels much like that which could be obtained of the 

 underlying strata by scattered borings in a field, the rock conditions 

 under which it was desired to ascertain. The solitary stations could 

 usually be linked together with others not too far distant in space and 

 time to permit the obtaining of fairly reliable and accurate current 

 tendency diagrams. 



The three figures — 21 to 23 — that immediately follow page 74 

 are the salinity and temperature sections. These have been con- 

 structed for the places where lines of stations were taken nearlj^ at 

 right angles to the Grand Banks shelf. The information on which 

 they are based is found in the table of oceanographic station data, but 

 the figures make this information easier to grasp at a glance. In 

 fact the figures show the tendency of the cold fresh water from the 

 north to hug the Bank slope so well that there is no necessity for 

 making detailed comment here. 



Following the oceanographic sections come Figures 24 to 30, which 

 are the surface isotherm charts. These were drawn one for each 

 patrol cruise from information on hand at the end of the several 15- 

 day periods. The temperatures on which these maps are based were 

 for the most part sent in from passing vessels, though the patrol 

 vessels themselves on each cruise were able to supplement the surface 

 observations received by radio with their own observations made 

 along their tracks. The temperatures sent in by passing vessels are 

 carefully recorded and analyzed, as they afford the patrol valuable 

 information concerning currents and probable drift of ice. 



A tremendous volume of reports made the temperature conditions 

 of the surface waters particularly well recorded in the vicinity of the 

 United wStates-Europe tracks area. Ships on the Canada-Europe 

 tracks sent in many temperature reports also, but only sparse reports 

 came from the band between these two main traffic lanes. 



When the F and B tracks are in use, as they normally are a large 

 part of the ice season, the seldom traversed ocean band between the 

 lanes averages about 300 sea miles wide. Poorly covered for water 

 temperatures means to the patrol poorly covered for ice conditions 

 also. It is this band of ocean intermediate between the great traffic 

 lanes that the ice-patrol vessel regards with much suspicion and to 

 which a great deal of time for scouting for bergs must be given. 



