BKIDGMAN. — WATER UNDER PRESSURE. 503 



process was observed There was a sudden increase of pressure, fol- 

 lowed by a slow fall past the equilibrium value VI-L to a final sta- 

 tionary value several hundred atmospheres lower down. This second 

 stationary pressure had all the properties of a new equilibrium pressure, 

 since the pressure was automatically restored to this value after 

 withdrawal of the piston. After sufficient withdrawal of the piston, 

 the pressure dropped in the normal way. The explanation, in view 

 of the facts as they now appear with the complete diagram before one, 

 is that ice VI at —8° was unstable. It had partly melted when it 

 flashed suddenly into V with increase of volume and increase of 

 pressure. The form V now found itself in the presence of water beyond 

 the equilibrium curve. The water froze to V with decrease of pressure 

 back to the equilibrium curve V-L. At the time, however, this expla- 

 nation was adopted with considerable hesitation. No experience had 

 been had of the very high reaction velocity possible between solids. 

 After this set of readings, pressure was left at 2000 kgm. over night, 

 the temperature graduaUy rising. 



The next morning another run was made at —6°. The liquid froze 

 to VI at —6° perfectly properly, with no trace of V. Pressure was in- 

 creased considerably beyond the equilibrium value at —6° and then 

 decreased. On the way down a new transformation point was found 

 at pressures higher than either the VI-L curve or the supposed V-L 

 curve. The new reaction ran with unusual velocity, equilibrium being 

 attained in the time usually required for temperature equilibrium. On 

 decreasing pressure further, the VI curve was passed over without in- 

 cident, but a new equilibrium pressure was found lower down on the 

 prolongation of the probable V-L curve of the day before. The expla- 

 nation suggested itself that the upper transformation point was on the 

 V-VI curve, the lower on the V-L curve. Some slight irregularities 

 in the data made it desirable to dismount the apparatus after this run. 

 During these experiments, the water had been enclosed in a glass bulb, 

 as this was one of the series of experiments to detect if possible any 

 effect of the transmitting liquid on the water. The glass bulb was 

 found crushed to fragments, evidently because of the reaction between 

 two solid phases with sudden increase of volume. 



In the apparatus as set up next time, the glass bulb was discarded, 

 therefore, and the water placed directly in a shell of copper. With this 

 apparatus no trace whatever could be found of the new phase V. 

 Measurements were made on the equilibrium and change oif volume 

 VI-L to temperatures as low as —20°. Lower temperatures could 

 not be easily attained because of the trouble with the CaCla cooling ar- 

 rangements. The subject was then dropped for a couple of months ; 



