320 THE DEPTHS OF THE SEA. (CHAP. VII. 
The sounding at Station No. 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 which 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°°1 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 lght 
upon the physical conditions of a hitherto unknown 
world. 
