396 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



given in Table IX. R is the resistance of the mercury reduced by 

 taking as unity the resistance of the liquid at atmospheric pressure 

 and the corresponding temperature. R for the liquid was obtained by 

 extrapolating beyond the freezing point to the pressure at which the 

 resistance of the solid was measured. The resistance of the soHd shows 



TABLE IX. 



Change of Electrical Resistance when Mercury Ch.a.nges from the 

 Liquid to the Solid at V.\rious Pressures. 



a distinct tendency to become less at the higher pressures and tem- 

 peratures. The effect of temperature only would be to raise the resist- 

 ance. The pressure coefficient of resistance must be negative, there- 

 fore, as for all other pure metals, and must have a value at least such 

 that 200 kgm. increase of pressure produces a greater fall of resistance 

 than 1° rise of temperature produces rise of resistance. This means 

 that the pressure coefficient of the solid is greater than 0.0004/200 = 

 0.000002. The table also makes evident the tendency of the change 

 of resistance liquid-solid to become less at higher pressures and tem- 

 peratures. This indicates that the effect of pressure on the resistance 

 of the li(iuid is greater than the effect on the solid, as one would expect, 

 although the reverse is true for the temperature effect. This enables 

 an upper limit to be placed on the pressure coefficient of the solid, since 

 the coefficient of the liquid is known. This upi)er limit is about ten 

 times the lower limit set above. It hardly seems worth while to at- 



