BREDGMAN. — MEASUREMENT OF HYDROSTATIC PRESSURES. 343 



shown that a manganin resistance gauge may be calibrated without 

 direct reference to an absolute gauge. 



This investigation was a necessary preliminary to the measurement 

 of various thermal properties of mercury and water under pressure, the 

 expenses of which have been partially defrayed by several liberal ap- 

 propriations from the Rumford Fund of the American Academy of 

 Arts and Sciences. 



Jefferson Physical Laboratory, 



Harvard University, Cambridge, Mass., 



October, 1911. 



