101 



7 to 10 day periods mentioned above represent the estimated time 

 lapse which the writer considers permissible for a set of observations 

 taken under the usual conditions that prevail in the various 10,000 

 square geographical mile areas located over the deep water just east 

 and southeast of the Grand Banks. 



A case of shift of position of water masses due to time lapse can be 

 seen when stations 1078 and 1091 are compared. These were 

 occupied within 10 miles of each other, but the interval of 21 days 

 between them prevents a reasonable dynamic comparison of the two 

 water columns. In the period between the taking of the first and 

 second of these stations a lighter water column appears to have pushed 

 inshore toward the eastern edge of the Banks. The warming of the 

 surface layer can be attributed to seasonal effects, but this cause can 

 not explain the large temperature rise of the 125 and 50 meter levels. 

 The salinities at all levels above 750 meters are much alike at the two 

 stations. The considerable difference in temperature values at some 

 levels can best be explained by postulating an inshore invasion of 

 warm water. 



Fifty stations, taken within the stipulated 7 to 10 day period, are 

 about the minimum number that can give a current map of a 10,000 

 square sea-mile area of sufficient accuracy to be of much real practical 

 value to the ice patrol. From the experience of the past four years 

 it is known that 50 stations, arranged in five rows 20 miles apart, with 

 10 stations in each row spaced at intervals averaging 10 miles, would 

 suffice to give a dynamic current map showing in some detail the 

 complicated local currents of a 100 sea-mile square area. 



When completed, the dynamic current maps are interpreted much 

 like weather maps, but the stations must be placed much closer 

 together than the Weather Bureau's observing stations if the compli- 

 cated detail of the water circulation is to be caught. They must be 

 spaced much closer about the Grand Banks region than similar ocean- 

 ographic stations taken for like purposes in parts of the ocean where 

 erratic currents due to mixture of radically different water masses are 

 absent. 



The hydrographic station values need not be regathered so fre- 

 quently as meteorological observations at weather stations. It is 

 well that this is so because it is much more tedious and difficult to 

 get the required dynamic data properly at an oceanographic station 

 than it is to observe the meteorological elements at an ordinary 

 Weather Bureau station. The great mobility of the atmosphere 

 requires the weather map to be remade from the synoptic data every 

 12 hours and in the sea off the Grand Banks where the currents 

 are especially complicated and interlocking, the stations must be 

 taken, as stated previously, within a 7 to 10 day period and com- 

 paratively close together to get the full story of the sea-water inter- 



