384 PROCEEDINGS OF THE AMEKICAN ACADEMY. 



or even higher, without serious difficulty. This accompUshed, he 

 was able to enter upon a series of researches upon the phase rela- 

 tions (volume-pressure-temperature) of water in its liquid and solid 

 states as well as those of certain other liquids, with results which 

 widely transcend in extent and value all that had been reached by 

 earlier researchers. He designed a direct primary pressure gauge 

 of very simple construction, and secondary gauges based upon the 

 change of resistance of mercury or manganin calibrated by the 

 former were also employed. 



A brilliant series of experiments was made by which were 

 studied the thermodynamic properties of liquid water up to 80 

 degrees temperature and 20,000 kg /cm- pressure, and also those 

 of five forms of ice, that is, forms which have different and novel 

 phase relations. Two of these were newly discovered by ]\Ir. 

 Bridgman. 



Studies were made of various other liquids and the changes of 

 phase under pressure of eleven chemically different substances 

 were likewise ascertained. 



The interesting and important fact is indicated by the cur^■es of 

 Professor Bridgman that for the passage from the solid to the liquid 

 state there is no critical point, a complete difterence from that 

 which occurs on the passage from the liquid condition to that of 

 vapor. 



In later papers a study of polymorphic changes is described with 

 important results, and an investigation of the electric properties 

 of metals under pressure, which subject is still occupying Pro- 

 fessor Bridgman's attention, except as it has been interrupted by 

 duties incident to the Great ^Yar. 



^Moreover, Professor Bridgman has not confined himself to pure 

 experimentation, Init has considered analytically the thermody- 

 namics of the subject which he has investigated. 



The llumford Committee considers itself fortunate to ha\e been 

 able by its grants to aid the researches of Professor Bridgman and 

 so to fulfill the desire of the Su])reme Court of the Counnonwealth 

 that appropriations made from the Rumford Pinid for researches 

 may lead to the award of the Rumford Premium. 



The ])resentation of the medals was made by the President to 

 Dr. Bridgman, who expressed his appreciation of tlie honor. 



