CHAP. VII. DEEP-SEA TEMPERATURES. 29] 
water on the outer shell, and thus protecting the 
bulb within. 
Mr. Casella was directed to construct some ther- 
mometers on this plan, only instead of 
being filled with air, the outer shell 
was nearly filled with alcohol warmed 
to expel a portion of the remaining 
air, and the chamber was then her- 
metically sealed, leaving a bell of air 
and vapour of alcohol to yield to the 
pressure and relieve the bulb within. 
The ‘ Miller- Casella’ thermometer WEVA 
proved so nearly perfection that it was “=| || 
decided to adopt it in future, and to |—3]} 
use it as a standard in a series of 
experiments which were undertaken 
to test the ordinary Six’s thermo- 
meters of the Hydrographic Office 
pattern. We depended upon this 
thermometer alone in our subsequent 
cruises in the ‘Porcupine, and we 
found it most satisfactory. During the 
summer of 1869 temperature observa- 
tions were taken at upwards of ninety 
stations, at depths varying from 10 to Sf 
24302 fathoms. Two thermometers, “S43 ™ Mier 
Casella modification 
CA.LONDON, 
UT. CASEL 
e 
o 
\ 
ili 
———$——| 
. of Six’s self-regis- 
numbered 100 and 103 respectively, tering thermometer. 
© ‘he large bulb is 
were sent down at every station, and double, witha layer 
in no instance did they give the least . Bis to slew 
reason to doubt their accuracy. Every “ 
observation was taken by Captain Calver himself, 
the lead with the thermometers attached being in 
every single instance let down by his own hand, 
wae 
