84 
Proceedings of Royal Society of EdinhurgJi. [dec. 19 , 
The body is possibly a tertiary phosphine oxide containing both 
aromatic and fatty radicals. 
We have repeated some of the experiments described in this 
paper, and hope to be in a position to publish the results 
shortly. 
5. A Criticism of the Theory of Subsidence as explaining 
the Origin of Coral Reefs. By H. B. Guppy, Esq,, 
M.B., RK Communicated hy Dr H. Mill. Published in the 
Scottish Geograjphical Magazine. 
6. On the Compressibility of Water and of Different 
Solutions of Common Salt. By Prof. Tait. 
[Ahstract.) 
Within the limits of the experiments, which were for t from 0° C. 
to 15° C., and forp from 1 to 3 tons-weight per square inch, it was 
found that the average compressibility of water per atmosphere may 
be fairly represented by 
0-28 
(36+p)(150 + ^)’ 
a formula which, while very convenient for application in the 
hydrostatic equations, extends to the whole range of temperature 
and pressure ordinarily occurring in nature. 
Some speculations, connected with Laplace’s theory of Capillary 
Action and with the Kinetic Theory of Gases, are given as to the 
meaning of the 36 tons-weight per square inch which occurs in the 
formula. 
Similar experiments made on solutions of common salt, of various 
strengths up to saturation, give analogous formulae. As a rough 
indication of the results, it may be stated that at 1° C. the average 
compressibility per atmosphere for the first 150 atmospheres is 
somewhere about 
0-002 
40-l-s 
where s is the mass of salt dissolved in 100 of water. 
