NEW METHOD FOR DETERMINING COMPRESSIBILITY 



weight of mercury W in order to reduce all the results to a compar- 

 able basis, namely, the results which would have been obtained if the 

 jackets had each held only a gram of the metal. The fourth column 

 contains this quantity with an added quantity a n constant with each 

 series. This a n is necessary to reduce these measurements beginning 

 at various pressures to the same starting point. The method of doing 

 this is explained in the following paragraph. 



Compression of Mercury in Glass. 



The results are best compared by graphic method, hence a diagram 

 is given herewith (Fig. 4). The portion of the curve below 37 atmos- 

 pheres is extrapolated (a proceeding which is indicated by the dotted 

 line) and the second, third and fourth series are begun intentionally on 

 the curve of the first, a is in each case the ordinate corresponding to 

 the first pressure of each series. Hence the lowest four points are 

 fixed arbitrarily and the agreement of the results is shown only by the 

 seven points at the pressures above 200 atmospheres. This agreement 

 is nevertheless close enough to satisfy the most exacting requirements of 

 the present work. The third series of experiments was made by Mr. 

 Frederick Bonnet, Jr. 



This curve represents various values of /3' /3", or the differences 

 between the compressibilities of glass and mercury at different pres- 

 sures, both being at 20 . After having been plotted several times on 

 a large scale, the most probable values for this quantity were found 

 from the averages to be those recorded on page 20. 



Thus there is a steady decrease in the value of (/3' /S") as the pres- 

 sure decreases. Without further data it is impossible to determine how 

 much of this decrease is due to the glass and how much to mercury ; 



