INTERNATIONAL CONVENTION SAFETY OF LIFE AT SEA. 



241 



the reading taken at that hour, say 755.7 mm., with a reading taken at 5 a.m., say 759.3 

 mm. In this case the barometric tendency would be expressed by a fall of 3.6 millimeters. 

 As a general rule the barometric tendency is to be determined from the trace of the baro- 

 graph. 



The barometric tendency is coded in two figures, according to the following table : 



Code XI. — Sea-surface temperature. 



Sea-surface temperature to tenths of a degree centigrade, is coded by three figures, or, 

 when necessary, by two figures preceded by zero. If the temperature is negative, the first 

 of these three figures is 5. For example : 



— 2.2° C. is coded as 522. 



+ 1.0° C. " 010. 



+ 15.6° C. " 156. 



