Rankine, was therefore much vivified by Lord Kelvin's specification (Comptes Rendus, 1889) of a material gyrostatically constituted medium which would possess this character.

This partition is termed the specification of the separation.

These steps may be traced in the gradual specification of the term.

In the specification of the patent applied for on the list of July 1877 he showed a sketch of an instrument which consisted of a diaphragm, with a small platinum patch in the centre for an electrode, against which a hard point, made of plumbago powder cemented together with india-rubber and vulcanized, was pressed by a long spring, the pressure of the carbon against the platinum disk being adjusted by a straining screw near the base of the spring.

The apparatus described in the patent specification is an iron cylinder heated by gas rings below, with a narrower cylinder beneath, through which passes upwards a stout iron cathode rod cemented in place by caustic soda solidified in the narrower vessel.