292 



THE DEPTHS OF THE SEA. 



[chap. VII. 



and I have always regarded it as a remarkable 

 evidence of my friend's care and skill that he 

 landed those two precious instruments at the end 

 of the year safe back, at Woolwich. 



Kg. 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 liable to 

 get jammed in the case. The scale 

 I jH I ^ is of white porcelain, graduated to 

 9 Pahrenheit degrees; the large bulb 



*S|[] is enclosed in an outer shell three- 



uB, I fourths filled with alcohol and her- 



metically sealed. It is right to 

 mention that I am informed by 

 Sir Edward Sabine that the ther- 



rG. 5t. — Copper case fnr , i i o • t i -r> 



protecting the Miuev- momctcrs used by Sir John Koss 



Casellathermometer. The . - . ^ , 



ends of tiie case above and m his Arctic vovaffe lu 1818 Were 



below are perforated to «/ o 



topls%reeiy throu^,"'"' protcctcd somcwhat on the same 

 principle, and that a thermometer 

 for resisting pressure was constructed under the 

 directions of the late Admiral Pitzroy, 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- 



FrG 



