Contents li 



PAGE 



glass of which it was constructed was determined by 

 one measurement. 



Method of using the piezometer, and results obtained 373 



The principle of this piezometer was embodied in 

 an instrument of precision constructed in 1880 . . 374 



The pressure in this hydraulic apparatus was 

 measured by water-piezometers which had been ex- 

 posed to measured columns of sea-water of known 

 density 375 



In the Pacific the average density of the sea-water 

 is such that a column of it, ten metres in height, exerts 

 a pressure of one atmosphere ... 376 



The two micrometers verified at the National 

 Physical Laboratory. 



In experiments with this instrument the effect 

 observed is the lengthening of the rod or wire when 

 the pressure is relieved ... . 377 



Description of the "creep" of the rod or wire . 378 



Advantage of having a very slight leak in the ap- 

 paratus 3** 



Specifications of the metals and wires experimented 

 with. 



The absolute linear compressibility of platinum . 382 



The absolute linear compressibility of gold and 

 copper . . 383 



The absolute linear compressibility of aluminium 

 and magnesium ........ 384 



Summary J results ...... 385 



The compressibility of these five metals im Teases 

 as their density and atomic weight dininish 



Particulars of the working of the instrument and 

 the expenditure of glass terminals. 



Microseismic effects produced in some wire-, when 

 a glass terminal IM . .... 387 



This effect very marked in the case of copper and 

 .:n. hut not in the case of platinum 



Special ilir-cti<m-. about fitting the fjass tnnnn.il>. 



Postscript. Loan of mv instrument i<> Professor 

 linbur^h l.r detn mm.itiou of the absolute 

 COmpressibihtx ot the; 1 : :neh the tluTin-'m 



used in the "Challenger" were made .... \^) 

 -on for request of the ! 



Instrument immediately fcnUtfeRtd tO the I'm-- 



