292 THE DEPTHS OF THE SEA. [CHAP. VI. 
and I have always regarded it as a remarkable evi- 
dence of my friend’s care and skill that he landed 
those two precious instruments at the end of the 
year safe back at Woolwich. 
Fig. 53 represents the latest im- 
provements on the Miller-Casella 
modification of Six’s self-registering 
thermometer. The instrument is of 
small size, to reduce as far as pos- 
sible the friction in passing through 
the water. The tube is mounted in 
ebonite, to avoid the expansion of a 
wooden mounting in the water, by 
which the instrument is lable to 
get jammed in the case. The scale 
is of white porcelain, graduated to 
Fahrenheit degrees; the large bulb 
is enclosed in an outer shell three- 
fourths filled with alcohol and _her- 
metically sealed. It is right to 
inention that I am informed by 
Sir Edward Sabine that the ther- 
‘protecting the “ite. Mometers used by Sir John Ross 
Casellathermometer. The 
ends ofthecaseaboveaud yn his Arctic voyage in 1818 were 
below are perforated to 
allow a current of water 
fom fesy tion, ~»~=6Protected somewhat on the same 
principle, and that a thermometer 
for resisting pressure was constructed under the 
directions of the late Admiral Fitzroy, at the 
suggestion of Mr. Glaisher, which differed from 
the Miller-Casella pattern in little else than the 
outer shell being partially filled with mercury 
instead of alcohol, and in being somewhat less 
compact and more fragile than the latter instru- 
