366 
PROFESSOR A. M. WORTHINGTON ON THE 
to eliminate the effect of the yielding of the glass itself, and which could not be made 
if the vessel were broken.* 
The vessel was therefore opened, and the alcohol in it subjected to a pressure of 
12*38 atmospheres in excess of the external atmospheric pressure, corresponding to 40 
tonometer divisions, and the apparent compression of the liquid was observed. The 
measures of the retreat of the end of the column along the tube were 
millims. 
28*19 
27- 53 
28- 36 
28-02 
27-05 
27-6 
(Specially trustworthy) 27'78 
Mean . 27 79 
The observed apparent extension in the same vessel under an equal tension, as given 
by the line of the diagram, is 27*8 millims. The closeness of the agreement is, of 
course, in part fortuitous, for the line of the diagram cannot be placed with extreme 
precision; but the practical coincidence of the two numbers is a very satisfactory 
confirmation of the view that the observations correspond to a straight line, and, 
since the small yielding of the nearly rigid glass vessel must be proportional to the 
stress, permits us to draw the conclusion that in the neighbourhood of the zero pressure 
the absolute coefficient of volume elasticity of alcohol is the same for extension as for 
compression, and so far as the observations show is constant between a pressure of 
+ 12 and — 17 atmospheres. 
The best way to obtain the absolute value of the coefficient is probably by direct 
experiments on the compressibility of alcohol in the neighbourhood of the zero point. 
The value given in L upton’s tables is per 10 6 grms. per sq. centime, or "0000906 
per atmosphere of 1033 "3 grms. Mr. Skinner by recent experiments made in the 
Cavendish Laboratory on alcohol at 13°"5 C. between 1 atmosphere and 1"3 atmo¬ 
spheres obtains the value '000093 per atmosphere. 
It seemed desirable, if only to serve as a check on the experiments, to mention 
the attempt that I made to determine directly the yielding of the glass vessel. For 
this purpose the alcohol was boiled out until only a very small residue was left, when 
mercury was allowed to enter which completely filled up the whole instrument. This 
mercury, whose compressibility is some fifty times less than that of alcohol, was then 
* As a matter of fact, the stem HE was unfortunately broken in setting up the apparatus for exhibi¬ 
tion in the rooms of the Royal Society, at the Soiree of June 18, 1890, but this was afterwards 
repaired without any interference with the neighbouring bulb. 
