In the undulator apparatus, which is similar in general principle to the " siphon recorder " used in submarine telegraphy, a spring or falling weight moves a paper strip beneath one end of a fine silver tube, the other end of which dips into a vessel containing ink.
The short leg of the siphon tube dips into an insulated ink-bottle, so' that the ink it contains becomes electrified, while the long leg has its open end at a very small distance from a brass table, placed with its surface parallel to the plane in which the mouth of the leg moves, and over which a slip of paper may be passed at a uniform rate, as in the spark recorder.
Into the solution dips a silver plate wrapped in filter paper, and the current is passed from the silver plate as anode to the bowl as cathode.
The plain lying between this coast range and the Andes dips below sea-level in the gulfs of Ancud and Corcovado (average width, 30 m.).
The chain dips below the water, then rises into the furnace and passes down into the other trough on its way out.