Note on the determination of the volume elasticity of elastic solids.

In a recent paper Mr. A. Mallock gives an ingenious and simple method of determining the coefficient of volume elasticity (bulk modulus) of metals by direct observation of the extension of a hollow right circular cylinder under uniform internal pressure. The method depends on a result of the mathematical theory which seems capable of being proved in a more direct and complete way, but which at the same time requires to be restricted by conditions to which Mr. Mallock does not seem to refer. Further, the method is only one of several which seem equally worthy of consideration.