Cross-section diagram of Varley's double-cup insulator for suspending telegraph wires. It consists of two distinct cups ("c", "C"), which are moulded and fired separately, and afterwards cemented together. The double cup gives great security against loss of insulation due to cracks extending through the insulator, and also gives a high surface insulation. An iron bolt ("b") cemented into the centre of the inner cup is used for fixing the insulator to the pole or bracket. It is a very serviceable pattern, though possessing the defect that the porcelain cup is not removable from the iron bolt on which it is mounted.