46 A Retrospect of Oceanography 



some thermometers reversing by messenger to test cases where 

 from the indications of the maximum and minimum thermo- 

 meter the law of decrease of temperature with increase of 

 depth seems to be departed from. 



Samples of intermediate water were collected at depths 

 of 800, 400, 300, 200, 100, 50 and 25 fathoms, and a separate 

 operation was required for each depth. At a full station 

 this necessitated the handling of 1875 fathoms of line. This 

 service was performed without the loss of any material whatever. 



The mean depth corresponding to 251 soundings with 

 temperatures, tabulated in the Report on Deep-sea Tempera- 

 tures, is 2060 fathoms, and 403 separate observations of the 

 temperature at the bottom were obtained. All the accidents, 

 excepting two, happened to the sounding-line in the first 

 sixty of these soundings, namely before, and including, the 

 i6th August, 1873. At the beginning of the voyage only one 

 thermometer was used at each sounding and exactly sixty 

 temperature observations correspond to these sixty soundings. 

 The breakages of the sounding line which occurred during this 

 period occasioned the loss of eleven thermometers, and this 

 was due principally to the use of the inferior sounding-line 

 (No. 2) during the first months of the voyage. 



At almost every one of the remaining soundings, 191 in 

 number, two thermometers were used. The exact number 

 of individual observations of temperature at the bottom was 

 343. We have seen that during this time, from August 1873 

 to the end of the voyage in May 1876, only two sounding- 

 lines were carried away, namely, those of the I4th and i6th 

 June, 1874, entailing a loss of four thermometers. Therefore, 

 in two years and nine months, 343 independent observations 

 of the temperature at the bottom, in an average depth of 

 2060 fathoms, were made at an expenditure of four thermo- 

 meters. This is at the rate of, in round numbers, 86 determina- 

 tions per thermometer lost. After leaving New Zealand, 

 the whole of the exploration of the Pacific Ocean, occupying 

 eighteen months, was carried out without the loss of a sounding- 

 line or of a thermometer, or other instrument attached to it. 

 One thermometer was lost by the parting of the temperature- 



