OCEANOGRAPHY OF THE PACIB^IC. i 



extreme rang-e of air temperature for any one daj^ was 14°, January 

 17, 1900. There is also one record of 13° August 30, 1899, four of 

 11°, and four of 10°. Averages are shown in the following- table: 



Average daily variations. 



How much the recorded air temperatures may have been aflfected by 

 local conditions, such as radiation from the heated deck at midday, or 

 evaporation from a wet deck, it is impossible to estimate. 



BOTTOM TEMPERATURES. 



No serial temperatures were taken. Observations of bottom tem- 

 peratures on both outward and homeward voyages to the number of 

 601 are reported. In drawing conclusions from the records of these 

 observations, some allowance should be made for the difficulties attend- 

 ing the measurement of temperatures at great depth, because of the 

 delicac}^ of the instruments, the enormous pressures to which they 

 are subjected, the shocks to which they are liable, and the vibration 

 tending to displace the index as the thermometer is drawn up. Pro- 

 fessor Tate says: ^^ " The circumstances under which thermometers are 

 let down and drawn up again at sea are extremely unfavorable to 

 accuracy of observation." In the column of remarks, on the Ne7'o 

 records, it is repeatedly noted that "Thermometer failed to work." 

 So that where striking variations from normal temperatures, at given 

 depths and in neighboring localities, appear on the record, the proba- 

 bilities seem largely in favor of the assumption of instrumental, or 

 possibly clerical, errors rather than of great eccentricities of tempera- 

 ture, unless there should appear to be something in the local condi- 

 tions reasonabl}^ to account for the variation. 



a Results of the Exploring Voyage of H. M. S. Challenger. 



