464 PROCEEDINGS OF THE AMERICAN ACADEMY. 



were made was placed in a steel shell, open at the top, and completely 

 surrounded by kerosene or gasolene by which pressure was transmitted. 

 Pressure was measured by observing the change of resistance of a cali- 

 brated manganin wire immersed directly in the same chamber with the 

 water. That the fluid transmitting pressure suffers no change of phase 

 which is accompanied by change of volume within the limits of meas- 

 urements was shown by direct experiment. Furthermore, that there 

 is no reaction under pressure between the water and the oil, which are 

 directly in contact, was shown by the sharpness of the freezing. See 

 Figure 31, page 515. The effect of an impurity is to make the discon- 

 tinuity less abrupt. In order to give additional evidence on this point, 

 in the course of the experiments the water was placed in shells of steel 

 or copper, directly in contact with kerosene or gasolene, in glass bulbs 

 directly in contact with kerosene, and in a glass bulb with a mercury 

 seal, the water coming in contact only with mercury and glass. The 

 results in all cases were identical. 



Three different forms of apparatus were used according to the tem- 

 perature range. The first, for the middle range from —25° to -}-20°, 

 was the same as that used in the work on mercury. It consisted 

 essentially of two parts: an upper cylinder in which pressure was pro- 

 duced by an advancing plunger, communicating through a heavy tube 

 with a lower cylinder containing the water under experiment and the 

 pressure measuring coil. The lower cylinder was placed in a thermo- 

 stat. The various sources of error and the corrections have been dis- 

 cussed in the paper on mercury. One correction had to be determined 

 anew, since the values used in the mercury paper were not for a cor- 

 responding range of temperature and pressure. This is the correction 

 for the thermal dilatation of the kerosene or gasolene which passes 

 from the lower cylinder at the temperature of the experiment to the 

 upper cylinder at the temperature of the room. The manner of de- 

 termining this correction was the same as before. One correction 

 applied to the results for mercury was avoided here, namely the cor- 

 rection for the variation in the room temperature. This was made 

 unnecessary by a water jacket at constant temperature placed around 

 the upper cylinder. 



The second piece of apparatus, for temperatures from —20° to —80'^, 

 was essentially the same as the first, consisting of two parts. But the 

 pressures for this temperature range are comparatively low, not reach- 

 ing over 4000 kgm., so that it was possible to make the lower cylinder 

 so small (1 inch o. d. by 8 inches long), that it could be placed in a 

 thermos bottle. The connecting tube was also made much smaller so 

 as to avoid conduction of heat into the thermos bottle. The method 



