118 



very little data collected from the ocean which throw much light on 

 this subject. In case we argue from the atmosphere we know that isb- 

 baric maps as much as 24 hours old contain little information on the 

 situation for the present. The scheme of oceanic circulation around 

 the Tail of the Bank this season altered quite noticeably within a space 

 of two weeks and then resumed, broadly speaking, its original state, 

 all within the priod of two months. It is hoped that the same plan of 

 oceanographic work introduced in 1926 is continued for a few years 

 so that we shall be in a position to say considerable more on the relia- 

 bility of current maps with the elapse of time. 



DISSIMILARITY BETWEEN DENSITY AND COLD WALLS 



The observations in 1926 corroborate earlier ones to the effect that 

 the density of the water around the Grand Bank is usually- higher 

 along the zone of contact between the Labrador current and the Gulf 

 Stream than on either side of the latter. But this density wall does 

 not exactly coincide in location with the zone of most abrupt transi- 

 tion from low to high temperature (the cold wall), but lies as a rule 

 25 to 35 miles inshore of the latter. Since the density wall unques- 

 tionably marks the boundary between the easterly and westerly sets, 

 this discovery means that the drop in the temperature of the surface 

 water near the continental slope does not mark the change in the 

 direction of the current. 



LIGHT WATER COLLECTS ON SURFACE OF THE SEA 



Evidence has been accumulating that there is a prevailing tendency 

 for relatively light water to collect on the surface of the sea immedi- 

 ately over the belt of the heaviest subsurface water, represented by 

 the density wall; this has been observed in the profiles of every ice 

 season since 1922, so it must be more than a coincidence. 



DRIFT OF BERGS CHECKED WITH CALCULATED CURRENTS 



We were handicapped this year by fog in comparing the drift of 

 the bergs with the currents calculated and plotted, but the few 

 examples obtained have been found to harmonize. (Fig. 21, p. 73.) 

 The fact that there were few opportunities to make comparisons in 

 the case of specific bergs ought not to be interpreted as detracting 

 from the value of the three sets of illustrations represented by Figures 

 49, 53, and 57, all of which were continually consulted by those in 

 charge of maneuvering the patrol ships. 



/W 





