NARRATIVE OF THE CRUISE. 



91 



temperature, to test its accuracy, for had it given the same result as the Miller- 

 Casella, it would have been a conclusive proof that the water was warmer below the 

 depth of minimum temperature, instead of, as was supposed, remaining at that tempera- 

 ture. This time, however, when hove to the surface, the cogwheel attached to the 

 propeller was missing, and the thermometer was in the same position as it was 

 when sent down, consequently it did not register. On February 12, 1875, the machine 

 being again in working order, the observations were proceeded with. The apparatus 

 was first sent to the bottom in 2550 fathoms, No. 18 thermometer being again used, and 

 it was afterwards sent to less depths with the following results : — 



" From this date the experiments with this instrument were continued as opportunity 

 offered ; the results are embodied in the table on the next page. 



" It will be seen from the above and following tables that four thermometers have 

 been under trial on board, Nos. 18, 30, 77, and 152, and that observations with each 

 instrument have been taken at various depths, the results being briefly as follows : — With 

 No. 18 five observations were made, four of which gave a higher reading than the 

 protected Six thermometer, and one a lower reading ; with No. 30 twelve observations 

 were taken, ten of the results being higher than those obtained by the protected Six, 

 and two lower; with No. 77 six observations were obtained, all the results being higher 

 than those obtained by the protected Six; and with No. 152 twenty -five observations 

 were obtained, ten of which were higher than the protected Six, fifteen of them agreeing 

 within 1° with the results given by that instrument, and none being lower. Of the 

 fifteen results given by No. 152, which agree so closely with the protected Six observations, 

 it will be noticed that ten of them were taken at depths less than 400 fathoms, whilst the 

 ten results that disagree were, with one exception, taken at depths exceeding 400 

 fathoms. It will thus be seen that, of forty-eight observations taken with these 

 thermometers thirty were higher, three were lower, and fifteen similar to the observations 

 taken with the protected Six instruments at the same depth. 



" That the Negretti & Zambra instrument might occasionally show a lower tempera- 

 ture than the protected Six can easily be understood ; for, supposing them both to stand 



