296 THE DEPTHS OF THE SEA. (CHAP. VIL. 
This experiment at once proved the advantage of 
the encased bulb. It was repeated with other ther- 
mometers with the same pressure and for the same 
period of time, and it was found that while the mean 
difference of the encased bulbs was only 0°95, that of 
the ordinary deep-sea thermometers was, as in No. 57, 
7°25. It follows, also, from these experiments, that 
very nearly all the difference or error is due to pres- 
sure on the full bulb, and that by encasing that bulb 
we have a nearly perfect instrument. 
The next series of experiments was made to esta- 
blish a scale by which observations by the ordinary 
instruments might be approximately corrected for 
pressure. ‘The following table gives the errors of six 
thermometers at different pressures. The ‘ standard’ 
is an encased Miller-Casella, the last a register- 
ing minimum thermometer by Casella enclosed 
in a hermetically sealed glass tube on Sir William 
Thomson’s plan. 
Pressure | 
in Standard. No. 54. No. 56. No. 76. No. 73. Thomson. 
Fathoms. 
- > 
250)| 0-4.) O° SC.) 1° 0C | 0-7C)) 0-8 C tO 
500 | 0:4 fi 7 1°5 1-4 1:7 | 0=65 4 
aes) %o. | 99 2-2 2°3 2:5 | s0=0an 
1,000 0-8 2:9 2-9 a 9-7. Oe 
1,250 | 0-9 S50 ego padres ye Wem feo 
1,500 | 0-8 4-3 A> 3 8 Aza 4°3 | 0°38 
1,750 | 0-95 | 4-6 4-9 | 497. 9) 527m SG 
}2000:)1s1) |) 5-4 | 5:5 | 5:38 1) 6-4 ie 
2 250 1) len 6-2 6-0 6-0 | 6°8 | Oe8 
12,500 | 1-2 Too | 6% 6-5 | 726 | Org 
The mean difference for each 250 fathoms in each 
thermometer is as follows :— 
