112 C. Barus — Compressibility of Hot Water a/nd 



it from the maximum to zero, and 

 taking the mean volume changes 

 corresponding to a given pressure. 

 When the water does not attack the 

 glass, the fiducial mark (pressure 

 low) at the beginning of the series, 

 is regained at the end. When water 

 attacks glass there is much shifting. 

 The glass was common lead glass 

 and distilled water was used. 



4. My introductory work between 

 0° and 100° contains a mere corrob- 

 oration of some of the results given 

 in §2. As it is not exceptionally 

 accurate I will omit it here. 



5. In table 1, the symbols used 

 have the following meaning : L is 

 the observed length of the thread 

 of water, 6 its temperature, and t 

 the mean time of observation, v/ V 

 is the volume decrement due to the 

 pressure^?. Finally ft is the mean 

 compressibility;* i. e. ft^C^/p^v/V). 

 The first series of data were ob- 

 tained at 28°, the next seven series 

 at 185°. Unfortunately I did not 

 observe the time when ebullition 

 commenced, and some subsequent 

 dates are also lacking. After clos- 

 ing the experiments, I noticed that 

 a fine filament of the upper thread 

 of mercury, had run down into the 

 core of the solid silicate below it. 

 Possibly this means that there had 

 been progressive erosion due to 

 water intruding between the mer- 

 cury and the glass. In this respect 

 the observations are uncertain. § 7. 



6. To discuss these results I first 

 plotted ^/Fasa function of p, thus 

 obtaining a series of curves of some- 

 what irregular contour, the charac- 

 ter of which, however, is obvious. 

 This will be more accurately ob- 

 served by plotting ft as a function 

 of the length L of the column, since 

 the time data are incomplete. The 

 result is striking. It shows a mean 



*It would be useless to calculate (3 by more elaborate means. The correction 

 referred to at the end of this paragraph is such, that if applied, it would accentu- 

 ate the inferences of the text. Its small value appears in § 7. 



20CMu« 300 J\t^ 



