34 



XXXIX, 31-84, May 1926) for approjdmating the effect of the specific 

 volume of the water below the potential surface cutting the bottom at 

 the station of lesser depth has been used. In this modification it is 

 assumed that the bottom passes through the deepest even level for 

 which the dynamic calculations have been made. This assumption 

 has its greatest effect when a shallow station is compared with an 

 adjacent station at which the depth is actually far in excess of 1,000 

 meters, the depth at which it is assumed the water is motionless. 



Surface temperature data were collected on the General Greene, 

 and reports were also received from a large number of ships crossing in 

 the vicinity of the Grand Banks. Upon the basis of this information, 

 charts of the surface isotherms were prepared and are shown in figures 

 12 to 18. In these charts isotherms have been drawn for each 4° F., 

 such as 32°, 36°, 40° F., etc. The number of temperature reports 

 received is probably smaller than it woidd have been had the large 

 cutters been on duty. The reason for this is partly a lack of interest 

 on the part of some ships during a year when no ice is drifting into 

 the United States-European steamer lanes, and partly the feebler 

 output of the radio of the General Greene as compared with the larger 

 cutters. Nevertheless, a sufficient number of reports were received 

 on each cruise to permit the construction of an isothermal chart and 

 thus to enable us to follow, in some measure at least, the tendencies of 

 the advancing season. 



In figure 12 will be seen the surface isotherms for the period March 

 2 to March 9. Figure 13, for the period March 20 to 26, indicates a 

 strengthening of the Labrador current in both its eastern and western 

 branches and a cooling of the surface water over the Banks, although 

 the latter feature may be the result of vertical mixing rather than an 

 indication of a flood of water from the Labrador current. A whorl of 

 warm water southwest of the Grand Banks and another on the eastern 

 side of the Banks is to be seen. The eastern whorl persisted through- 

 out the season, and the chart for the period April 3 to 1 1 (fig. 14) shows 

 a general warming. Figure 15 for April 18 to 26 shows a continuation 

 of the gradual warming with no remarkable change in the extent of the 

 coldest water, except that between longitude 52° W. and 53° W. there 

 is a hint of an increasing intrusion of cold water to the southward of 

 the Avalon Peninsula. In figure 16, representing conditions for the 

 period May 6 to 17, this intrusion is more marked and its effect can be 

 traced through the south-southwestward embayment of the isotherms 

 even as far as about latitude 42° N., longitude 55° W. This period 

 was characterized by a succession of strong winds from the northeast 

 and southwest quadrants in the vicinity of Flemish Cap. This fact 

 probably contributed to the irregular east and west fingers in that 

 locality. Figure 17 showing the conditions for the period May 27 to 



