The central conductor is covered with several continuous coatings of guttapercha, the total weight of which varies between 70 and 650 lb to the mile.
The famous cameo glass was formed by covering a mass of molten glass with one or more coatings of a differently coloured glass.
For if C l and C2 are the capacities and Q i and Q2 are the charges after contact, then Qi/CI and Q2/C2 are the potential differences of the coatings and must be equal.
If a charged condenser is suddenly discharged and then insulated, the reappearance of a potential difference between its coatings is analogous to the reappearance of a torque In the case of a glass fibre which has been twisted, released suddenly, and then gripped again at the ends.
The blister if unbroken was heated, pricked, and then rubbed level with a burnisher; if, as sometimes happened, the silver had flaked away it was replaced by coatings of pure leaf silver rubbed in with a burnisher.