By the time the south-west half of the sea was surveyed in December 

 the surface temperatures had dropped about 1° c, so that the values 

 fell within the ranges 28-5° c. to 29-0° c. Because of this difference in 

 range during the two parts of the survey it was not possible to connect the 

 isotherms for the two halves of the ,sea. During the December survey 

 the temperatures were so uniform over the area that almost no isotherms 

 with 0-5° c. interval could be drawn. 



At 50 Metres (Chart 9). — At a depth of 50 metres this difference 

 in temperature for the October and December surveys is still apparent. 

 In the central part of the sea the difference in temperature between 

 the two areas is about 0-5° c. The temperature throughout the Sulu 

 Sea at 50 metres during the October and December surveys were fairJy 

 uniform, lying within the range 27-5° c. to 29-0° c. and were only from 

 0-5° to 1-0° lower than at the surface. No complex patterns had 

 developed. 



At 75 Metres (Chart 10). — The distribution of temperature at the 

 75-metre level shows two striking features. First, the general cooling 

 which took place in the surface laj^er between October and December 

 did not extend to this depth so that there is no difficulty in connecting 

 the isotherms for the October and December surveys. The second 

 feature is the complex temperature pattern as contrasted with the 

 distribution of temperature at the 50-metre level and at the surface. 



The pattern in general corresponds to the pattern of current eddies, 

 which were described above for the surface and 100-metre levels for this 

 season of the year. The South Central Eddy is characterized by low 

 temperatures ; the North Central Eddy by high temperatures. Each 

 of the other eddies is defined by characteristic isotherms. The highest 

 temperature at this level was 28-20° c. off southern Palawan, although 

 a temperature of 28-01° c. was found in the North Central Eddy. The 

 lowest temperature " at this level was 24-63° c. which occurred in the 

 South Central Eddy. 



At 100 Metres (Chart 11). — At the 100-metre level during the north- 

 east monsoon the pattern of temperature distribution resembled that 

 for the 75-metre level. The principal difference was a large centre of 

 water of low temperature in the North. This is an expansion of the 

 centre found somewhat more to the west at the 75-metre level. It 

 almost crowded out the centre of warmer water of the North Central 

 Eddy. 



The difference between the patterns in the western part of the Sulu 

 Sea for the 75-metre and 100-metre levels may be due to the fact that 

 temperature data are not available for station 57 below a depth of 75 

 metres. This station is at latitude 08° 32' N., longitude 118° 32' E. 



At 200 Metres (Chart 12).— Ai the 200-nietre level the complexities 

 so evident at the 75-metre and 100-metre levels have almost completely 

 disappeared. Throughout the whole sea the temperature is near 15° c. 

 and ] 6° c, except at one station in the north-west, where the temperature 

 was 17-52° c. 



Charts are not presented for levels below 200 metres. Temperatures 

 are very uniform at deeper levels in the Sulu Sea. At 400 metres the 

 range in horizontal distribution of temperature is less than l-5°c., 

 while at the 800-metre level the range is less than 0-1° c. 



240 



