No. 24. [From Proc. Roy. Soc. 1903, Vol. i.xxn. pp. SS 92.] 



ON A REMARKABLE EFFECT PRODUCED 

 BY THE MOMENTARY RELIEF OF 

 GREAT PRESSURE 



THE effect is shown in the brass tube and the copper sphere 

 which I have the honour to exhibit to the Society. It is also 

 illustrated in Figs. 1-4 which accompany this paper. 



The experiment was made for the first time on board the 

 "Challenger" in the early part of the cruise. At that time the 

 deep sea thermometers, with protected bulb, had only been 

 recently introduced, and the effect of pressure on thermometer 

 bulbs, whether protected or not, occupied public attention. 

 In the deepest sounding made by the "Challenger" in the 

 Atlantic, namely, that of March 26, 1873, when a depth of 

 3875 fathoms was reached, both the thermometers, which were 

 sent to the bottom, collapsed. It, therefore, became a question 

 what recommendation should be made to the thermometer 

 makers to assist them in producing thermometers which shall 

 be able to withstand the greatest pressure to which they are 

 likely to be exposed in the work of ocean sounding. 



For thU purpose I immediately prepared the following 

 experiment : I took glass tubes of three different calibres. 

 The widest had about the calibre of the outer bulb of a Millar- 

 Casella thermometer, the n. UK. west had an internal diameter 

 of 6mm., and the third had .\ diameter of about lomni. 

 A li ngth of 75 mm. of each was sealed up at both ends, and 

 e tubes were wrapped in a -Inth ami enclosed in the 

 cylindrical copper case of a deep-sea thermometer. 



The upper and lower ends of these cases are pier* d with 



many hdr- in nrdrr to permit the passage of water through 



i. On the next day, Y ;, 1873, the case was attached 



