Illustrated history of the United States mint / with a complete description of American coinage, from the earliest period to the present time

by Unknown

INGOTS.

These are stamped with their weight and value in the deposit room. The floors that cover the melting rooms are made of iron in honey-comb pattern, divided into small sections, so that they can be readily taken up to save the dust; their roughness acting as a scraper, preventing any metallic particles from clinging to the soles of the shoes of those who pass through the department, the sweepings of which, and including the entire building, averages $23,000 per annum, for the last five years.

The copper and nickel melting rooms, wherein all the base metals used are melted and mixed, is on the same side and adjoining to the gold and silver department. Up to the year 1856, the base coin of the United States was exclusively copper. In this year the coinage of what was called the nickel cents was commenced. These pieces, although called nickel, were composed of one-eighth nickel; the balance was copper.

The composition of the five and three cent pieces is one-fourth nickel; the balance copper. The bronze pieces were changed in 1859, and are a mixture of copper, zinc and tin, about equal parts of each of the two last; the former contributing about 95 per cent. There are seven furnaces in this room, each capable of melting five hundred pounds of metal per day. When the metal is heated and sufficiently mixed, it is poured into iron moulds, and when cool, and the rough ends clipped off, is ready to be conveyed to the rolling room.

The Rolling Room.

From the melting rooms through the corridor we reach the rolling room. The upright engine, on the right, of one hundred and sixty horse power, supplies the motive force to the rolling machines, four in number. Those on the left, are massive and substantial in their frame-work, with rollers of steel, polished by service in reducing the ingots to planchets for coining. The first process or rolling is termed breaking down; after that it requires to be passed through the machine until it is reduced to the required thinness—ten times if gold, eight if silver, being annealed in the intervals to prevent breaking. The rollers are adjustable and the space between them can be increased or diminished at pleasure, by the operator. About two hundred ingots are run through per hour on each pair of rollers.

The pressure applied is so intense that half a day’s rolling heats, not only the strips and rollers, but even the huge iron stanchions, weighing several tons, so hot that you can hardly hold your hand on them.

When the rolling is completed the strip is about six feet long, or six times as long as the ingot.

It is impossible to roll perfectly true. At times there will be a lump of hard gold, which will not be quite so much compressed as the rest. If the planchets were cut from this place, it would be heavier and more valuable than one cut from a thinner portion of the strip. It is, therefore, necessary to “draw” the strips, after being softened by annealing.