1 Contents 



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The pressure indicated by a manometer in the form 

 of a mercurial thermometer the bulb of which is ex- 

 posed to the pressure. 



The value of its readings determined by comparison 

 with those of a piezometer containing distilled water 

 which had been subjected to the pressure of measured 

 columns of sea-water in the "Challenger." 



Therefore, the pressures given in this paper are 

 absolute. 



Table I gives values of micrometer readings . . 360 

 Comparison of manometer with piezometers . . 361 

 Measurement of the rod and description of micro- 

 meters ....... . . . 362 



Description of Table II 363 



Table II. Details of experiments on glass rod . 364 

 Table III. Summary of experiments on the com- 

 pression of the glass rod ...... 368 



The absolute cubical compressibility of the glass 

 was found to be 2-92 per million ..... 369 



Remarkable crackling noise which accompanies re- 

 lief of pressure in a mixture of ice and water. 



Illustration of peculiar spherules produced in blocks 

 of ice under high pressure 370 



No. 26. ON THE COMPRESSIBILITY OF SOLIDS. [From Proc. 



Roy. Soc. 1904, Vol. LXXIII. pp. 296-310] . . . 371 



In the experiments described in this paper the 

 absolute linear compressibility of certain metals is 

 directly determined. 



History of the discovery of the experimental 

 method used . . ...... 371 



Date of the discovery, 23rd March, 1875, the day 

 on which the "Challenger" made her deepest sounding 

 in the Pacific and almost exactly the second anniversary 

 of her deepest sounding in the Atlantic. 



These two soundings occupy homologous positions 

 in the two oceans, that in the Atlantic about ninety 

 miles north of St Thomas, West Indies, and that in the 

 Pacific about the same distance north of New Guinea, 

 East Indies. 



Design and construction of the piezometer which 

 consisted of nothing but glass 372 



With it the absolute linear compressibility of the 



