370 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



mean of these five points was taken as the best point at this pressure. 

 Weights were assigned to the smooth curves obtained with each pie- 

 zometer inversely as the arithmetic difference between the observed 

 deviation points and the smooth deviation curve. The weights at 0° 



005 



2 3 

 PRESSURE , 



KGM/CM'XIO 



FiGtrRE~4. The results with the two best piezometers for the compressi- 

 bility of mercury at 0°. The right-hand vertical scale refers to No. 4, the 

 left-hand scale to No. 8, annealed. 



varied from 1 to 7. Finally, a parabola was passed through these best 

 points, the deviations of these weighted best points from the parabola 

 were plotted against pressure, and the smooth curve through these 

 deviations, together with the parabolic formula, was taken as giving 

 the best possible relation between change of volume and pressure. 

 This was the process used in the final determinations. It has been 



