1869.] adapted to Deep-sea Soundings. 485 



and not to any temporary change in the capacity of the bulb produced by 

 pressure. 



This will be rendered evident by an examination of the subjoined Table 

 of observed temperatures : — 



First Series : Pressure 2\ tons per square inch. 



Number of 

 Thermometer. 



Minimum index. 



Maximum index. 



Maximum 

 mercury. 

 After. 



Before. 



After. 



Before. 



After. 



Protected ... 9645 







47*0 



47-7 





„ ... 2 



470 



465 



• 46-7 



476 



46-5 



5 



47-0 



463 



46-5 



476 



460 











476 





Unprotected . 1 



46-7 



46-4 



46-5 



540 



46 



3 



47-0 



46-5 



46-5 



56-5 



46 



56 



470 



46-0 



470 



55-5 



46 



9651 







46-7 



118-5 





Mean 



46-9 



46-3 



46-7 





461 



Temperature of external air 

 Temperature of thermometer \ 

 in press J 



49 

 46-7 



49 

 47 





In the Phillips's maximum thermometer, with unprotected spherical 

 bulb, No. 9651, the bulb had experienced so great a degree of compression 

 as to drive the index almost to the top of the tube. In all the other un- 

 protected instruments, which had been made with bulbs of unusual thick- 

 ness, the index had been driven beyond its proper position from 6 0, 4 to 

 8°'9 F. ; and it is obvious that the amount of this error must vary in each 

 instrument with the varying thickness of the bulb and its power of resist- 

 ing compression. 



Notwithstanding the great pressure to which these instruments had been 

 subjected, all of them, without exception, recovered their original scale- 

 readings as soon as the pressure was removed. 



It will be seen that the mean rise of temperature indicated by the three 

 protected instruments was o, 9 F., whilst the mean depression registered 

 on removing the pressure amounted upon all the instruments which ad- 

 mitted of its measurement to 0°'6, an agreement as close as was to be 

 expected from the conditions of the experiment. 



A second set of experiments was made upon the same set of instruments, 

 with the exception of 9651 ; but the pressure was now raised to 3 tons 

 upon the inch ; this was maintained for ten minutes. When it had risen 

 to 2f tons a slight report was heard in the press, indicating the fracture 

 of one of the thermometers. On examining the contents of the press 

 afterwards it was found that No. 2 was broken, the others were uninjured. 



