90 



THE VOYAGE OF H.M.S. CHALLENGER. 



" The first time they were used was in the Sulu Sea, where the minimum temperature is 

 reached at a depth of 400 fathoms, and it was thought a good opportunity to try whether 

 the water at greater depths exceeded this temperature. The apparatus was consequently 



L 



— 1^ - — j 







SCALE OF INCHES 



Fig. 29. — A, C, Negretti k Zambra's Deep-Sea Thermometer ; B, Ferguson's modification. 



sent to the bottom, the depth being 2225 fathoms, and the thermometer (No. 18) 

 registered 54°, whereas the minimum temperature at 400 fathoms was 50°'5 ; the 

 temperature of 54° being at the depth of 190 fathoms by the Miller-Casella thermometer. 

 The same thermometer (No. 18) was next sent to 400 fathoms, the depth of minimum 



