46 THE LINEAR COMPRESSIBILITY OF COPPER AND IRON, 



G was a steel plate perforated through the center, set with its upper 

 surface level with the base of the water-jacket. The object of the plate 

 was to provide a solid support for the metal rod to be measured. 



This metal rod was electrically insulated by being surrounded with sev- 

 eral pieces of loosely fitting glass tubing (A r ). The lower end of the tube 



Fig. 7. Apparatus for Determining Linear Compressibility. 



incasing the base of the metal rod had been almost closed, so that the rod 

 rested on a thickness of 1 mm. of glass. The upper part of the metal rod 

 was somewhat larger in diameter than the shaft and contained on top a 

 ^hallow cup into which was placed a drop of mercury, intended to make 

 electrical contact with the platinum point F. This part of the rod was 



