340 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



There are various abnormalities besides those in the neighborhood of 

 0°, however, as will be shown by the other figures. 



With regard to the compressibility there seems to be some variance 

 of usage, so that it will be well to call attention to the fact that the 

 quantity used throughout this paper in the sense of compressibility is 



0.0*5 Iftr 



0123456789 10 U 12 

 Pressure, kgm. / cm.^ x 10^ 



Figure 4 The isothermal compressibihty of water, ( ^ j against pressure. 



the derivative ( -- ) . Sometimes the expression - ( r— ) is used in the 

 \dpjt V \dpjt 



same sense. Figure 4 shows the compressibility, that is, the analytic 



expression ( t- ) , as a function of the pressure at 0°, 20°, and 80°. 



It would have made the figure too crowded to have tried to show the 

 values for 40° and 60° also. The complete values for the five standard 

 temperatures are shown in Table V separately, however. The figure 

 shows the well known abnormality in the compressibility at the low 

 pressures, namely a higher compressibility at the lower than at the 

 higher temperatures. This abnormality disappears above 50°, and 

 from here on the compressibility increases with rising temperature. 

 The figure shows that at 80° the initial compressibility is higher than 



