74 



Set I. April 6 to 10, 20 stations. (Figs. 33, 34, 35, and 36.) 

 Set II. April 21 to 25, 21 stations. (Figs. 37, 38, 39, and 40.) 

 Set III. May 10 to 18, 59 stations. (Figs. 41, 42, 43, and 44.) 

 Set IV. May 29 to June 3, 31 stations. (Figs. 45, 46, 47, and 48.) 

 Set V. June 9 to 25, 68 stations. (Figs. 49, 50, 51, and 52.) 

 The dynamic maps. Figures, 33, 37, 41, 45, and 49, show the topog- 

 raphy of the sea surface compared to the 750 decibar (meters) 

 surface, the assumption being that this plane was level. The num- 

 bers, viz, 728.80, 75, 728.70, etc., represent the height of the surface 

 of the sea in dynamic meters above the 750 decibar base plane. 



j^U^ 



^W 



r' \ 



\ /, / 



726.60 



.4fc 



45 



128.70 



72S-50 



-725.00- 



40 



55 .52 S\ SO .*5> -46 -47 4-fo 



Fig. 33. — Set I. Dynamic topographic map drawn from observations made at stations 631-651, 

 April 6-10, 1927. This map is read the same as an ordinary isotaric weather map , 



Such maps are quite similar to the ordinary isobaric weather maps, 



and, for all practical purposes, the dynamic contours represent the 



stream lines of the currents, as explained in Coast Guard Bulletin 



No. 14. 



SET I 



The oceanic situation April 6 to 10 may be described as consisting 

 of an ellipitical depression in the sea surface centered over the south- 

 west slope of the Grand Bank. From this center a trough extended 

 to the eastward around the Tail, more or less paralleling the contour 

 of the slope, and separating water of higher elevation, which lay in 

 on the Bank, from that offshore to the southward. Figure 33 shows 

 that the sea surface was highest at a point about 100 miles southwest 



