392 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



polates almost linearly to the ordinary freezing point at —38°. 8 and 

 atmospheric pressure, it was not thought necessary to make the special 

 eflfort demanded to run a thermostat at temperatures below —15°. 



One other remote possibility of error was guarded against. The 

 capillaries containing the mercury were fine, the bore being about 



TABLE VIII. 



Freezing Pressure of Mercury at Different Temperatures by the 

 Method of Change of Electrical Resistance. Data of 1911. 



0.1 mm. It was thought barely possible that the curvature of the 

 surface might be sufficient to produce a rise of internal pressure in the 

 mercury sufficient to change slightly the external pressure required to 

 hold liquid and solid in equilibrium. This effect was shown to be 

 negligible by using two capillaries of different sizes, one three times 

 the diameter of the other. The equilibrium pressure found at 0° 

 with the larger capillary was 7680 kgm., and with the smaller 7660. 

 The divergence is in the direction to be expected, but it is of the same 

 order as the experimental discrepancies. The data of 1911 were ob- 



