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Mr. J. Y. Buchanan. On a Remarkable Effect [May 14, 



"On a Remarkable Effect produced by the Momentary Relief of 

 Great Pressure." By J. Y. BUCHANAN, F.E.S. Received 

 May 14 Read May 28, 1903. 



[PLA.TES 1 AND 2.] 



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 

 figures 14 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 intro- 

 duced, and the effect of pressure on thermometer bulbs, whether 

 protected or not, occupied public attention. In the deepest sound- 

 ing 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, there- 

 fore, 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 this 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 narrowest 

 had an internal diameter of 6 mm., and the third had a diameter 

 of about 10 mm. A length of 75 mm. of each was sealed up at 

 both ends, and the three tubes were wrapped in a cloth and enclosed 

 in the cylindrical copper case of a deep-sea thermometer. 



The upper and lower ends of these cases are pierced with many 

 holes in order to permit the passage of water through them. On 

 the next day, March 27, 1873, the case was attached to the 

 sounding line and a depth of about 2800 fathoms was reached. 

 When the case came up again it looked as if someone had struck it 

 in the middle with a hammer. When it was opened and the cloth 

 unfolded, it seemed for a moment as if it were full of snow, but a 

 second look showed that what appeared to be snow was nothing but 

 finely comminuted glass. The two wider tubes had collapsed, but 

 the narrow one was intact. At first sight the effect produced on the 

 copper case was puzzling, but after a little study and reflection its 

 nature became apparent. 



No account of the experiment has been published, and when I was 

 able, through the kindness of H.S.H. the Prince of Monaco, to join 

 his yacht the "Princesse Alice" for her cruise of last summer, I 

 determined to repeat it, and, if possible, to vary it. Owing to press of 



