356 On a Remarkable Effect produced by the 



expansion of the mass of compressed water in the copprr 

 sphere takes off from the suddenness of the action, while it at 

 the same time reduces, by at least one-half, the difference of 

 pressures outside and inside the sphere at the instant of collapse, 

 and this is the agent which deforms the metal sphere. 



By altering the relation between the volume of the copper 

 sphere and that of the glass sphere enclosed in it and the 

 pressure to which the system is exposed, the effect produced 

 may be varied at will. When experimenting in the sea, the 

 volume of the compressed water outside of the copper sphere 

 is practically infinite. If it is sought to reproduce these effects 

 in the laboratory, then a very large pressure vessel must be 

 used. If a pressure vessel of limited size be used and, altering 

 the experiment, if the hermetically sealed glass sphere and 

 the copper sphere with its polar perforations be placed in it 

 separately, then when the pressure is raised to such a point 

 that the glass sphere collapses, the copper sphere will burst 

 outwards. 



I was profoundly impressed at the time by the experiments 

 which I made on board the "Challenger," and I connected 

 them with another experiment which is familiar to chemists. 

 When substances are set to re-act upon one another in a sealed 

 tube, there is frequently disengagement of gas which produces 

 a very high tension in the interior of the tube even when cold. 

 If it is sought to open the tube by breaking off the sealed point, 

 an explosion is almost sure to take place. This may have very 

 serious consequences, and yet it has been produced by a relief 

 of pressure. These examples of the destructive effect which 

 can be produced by the sudden relief of pressure led me to 

 believe that many shocks of earthquake may be due to similar 

 relief of subterraneous pressure. 



These experiments, whether made with the copper ball or 

 with the brass tube, furnish striking demonstrations of the 

 importance of the element of time in all physical considerations. 



The collapse of the brass tube, under the peculiar circum- 

 stances of the experiment, is the exact counterpart of the 

 experiment which is frequently, but unintentionally, made by 

 people out shooting, especially in winter. If, from inattention 



