The subjection of the core to a hydraulic pressure of four tons to the square inch and an electric pressure of 5000 volts from an alternating-current transformer has been adopted, by one manufacturer at least, to secure the detection of masked faults which might develop themselves after submergence.
As an ordinary instance, it has been stated that the cost of repairing the Direct United States cable up to 1900 from its submergence in 1874 averaged £8000 per annum.
Cables have frequently been picked up showing after many years of submergence no appreciable deterioration in this respect, while in other cases ends have been picked up which in the course of twelve years had been corroded to needle points, the result probably of metalliferous deposits in the locality.
Marine deposits were laid down over the south of the state after a submergence of the region; an uplift afterwards made of these deposits a coastal plain.
When the warmer interglacial periods recurred the polar and continental ice-caps melted and the sea-level became raised again - that is, there was submergence of the eroded plateaux formed as indicated above.