320 THE DEPTHS OF THE SEA. [CHAP. vn. 



The sounding at Station Xo. 37, at a depth of 

 2,435 fathoms, has already been fully described as an 

 example of the most recent method of determining 

 extreme depths with accuracy. Two Miller-Casella 

 thermometers, numbered 100 and 103 respectively, 

 were lashed to the sounding-line in their copper 

 cases, one a little above the other, about a fathom 

 and a fathom and a half above the 'Hydra' sounding- 

 machine. These two instruments had been prepared 

 and tested with extreme care, and had been employed 

 throughout the first cruise ; their freezing-points had 

 been again verified at Belfast in case the enormous 

 pressure to w r hich they had been subjected might 

 have affected the glass, and we had absolute confidence 

 in their indications. The indices were set before the 

 instruments were let down at the temperature of the 

 surface, 21'l C., and 21'15 C. They were allowed to 

 remain at the bottom for ten minutes, and on their 

 return to the surface in upwards of two hours and a 

 half, they were unanimous in recording a minimum 

 of 1'65 C., the slight differences between the two 

 instruments, which gave the almost inappreciable 

 error for one of them of 0'05 C. at 21 C., being 

 imperceptible at the lower temperature. 



It had a strange interest to see these two little 

 instruments, upon whose construction so much skilled 

 labour and consideration had been lavished, con- 

 signed to their long and hazardous journey; and their 

 return eagerly watched for by a knot of thoughtful 

 men, standing, note-book in hand, ready to register 

 this first message, which should throw so much light 

 upon the physical conditions of a hitherto unknown 

 world. 



