In time it became a common practice to cover them with a thin sheathing or plating of iron, in order to add to their life; this expedient caused more wear on the wooden rollers of the wagons, and, apparently towards the middle of the 18th century, led to the introduction of iron wheels, the use of which is recorded on a wooden railway near Bath in 1734.
Care must be taken not to expose goods in the plating-bath to too high a current density, else they may be "burnt"; they must never be exposed one at a time to the full anode surface, with the current flowing in an empty bath, but either one piece at a time should be replaced, or some of the anodes should be transferred temporarily to the place of the cathodes, in order to distribute the current over a sufficient cathode-area.
Decorative plating-work in several colours (e.g.
The iron plating extended 2 ft.
Watt, Electro-Plating and Electro-Refining of Metals (London, 1902); W.
In 1788 the first woollen mill in New England was opened in Hartford; and here, too, about 1846, the Rogers process of electro-silver plating was invented.
Cruikshank was already experimenting with a process of electro-plating, and in 1837 Mr Spencer in England, and in 1838 Professor M.
In some cases the whole object is a modern reproduction in electro-plate, but more often really old articles from which the original plating has been worn off in course of time have been replated, both equally being in the eyes of the connoisseur, unworthy of serious attention and comparatively valueless.
In practice, however, it cannot be thrown down electrolytically with a dissimilar anode so as to win the metal, and certain difficulties are still met with in the analogous operation of plating by means of a similar anode.
Gilding, stains and lacquers, electro-plating, chasing, "matting," frosting, burnishing, mechanically produced mouldings and enrichments, and the other processes esteemed in the 10th century, are disused and avoided.
Shoe-making, tanning, agricultural trade, tin-plating, and the manufacture of confectionery and cider have superseded the former large woollen and serge industries.
Nickel is used for the manufacture of domestic utensils, for crucibles, coinage, plating, and for the preparation of various alloys, such as German silver, nickel steels such as invar (nickel, 35.7%; steel, 64.3%), which has a negligible coefficient of thermal expansion, and constantan (nickel, 45%; copper, 55%), which has a negligible thermal coefficient of its electrical resistance.
These genera attained the Colophiuran grade in respect of external plating, but it is unlikely that they or their ancestors had acquired even the Streptophiuran type of vertebra.