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PROCEEDINGS OF THE AMERICAN ACADEMY. 



exception at atmospheric pressure also holds under high pressure. This 

 is the fact that it is impossible to superheat a crystalline phase with 

 respect to the liquid phase, although the liquid may be subcooled. 



SLIDER DISPLACEMENT. MM. 



Figure 25. Shows on an enlarged scale the possibility of subcooling the 

 liquid but the impossibility of superheating the solid. The two curves have 

 been displaced, the one with respect to the other; the melting and freezing 

 actually takes place at the same pressure. One division on the pressure axis 

 corresponds to 40 kgm. 



sometimes very considerably, with respect to the solid. Figure 25, 

 drawn on a very large scale, shows this fact. At the lower corner the 

 subcooling of the liquid with respect to the solid is shown, while at the 

 upper corner, where the pressure is decreased on the solid phase, is 

 shown the sharp change of state when the equilibrium pressure is over- 

 stepped. The slight irregularities in the points are due to errors of 



