Page:The American Cyclopædia (1879) Volume XI.djvu/636

 G18 MINT sons to be communicated by him to the senate. The officers of each mint are a superintendent, an assayer, a melter and refiner, and a coiner, and for the mint of Philadelphia an engraver. The following are the usual forms in which gold bullion is received: lumps, grains, and dust in their native state ; amalgam with the quicksilver burned off; foreign coin, United States coin issued before 1834, and United States defaced coin issued since ; jewelry, den- tists' plate, bars, rings, &c. The following are the usual forms in which silver bullion is received : foreign coin, United States coin issued before 1853, and United States whole dollars and de- faced coin issued since ; plate, bars, rings, &c. ; native lumps and grains in their native state ; and, as an accommodation to the holders, the coppery silver of Lake Superior, but it must contain at least one fourth silver. Deposits of bullion, not less than $100 in value, are receiv- able by the superintendent, who causes it to be weighed in the presence of the depositor, and gives him a receipt therefor expressing the weight in troy ounces. Each deposit is kept separate during the process of melting and as- saying, and until its precise value is determined. This is generally accomplished in three days, when, on presentation of the original receipt, the net proceeds are paid to the depositor or his order. The charge for converting standard gold bullion into coin is one fifth of 1 per cent. ; and the charges for converting standard silver into trade dollars, for melting, refining, tough- ening, &c., are fixed from time to time by the director so as to equal but not to exceed the actual average cost. Deposits of gold are paid in gold, and if the deposit contains the value of over one dollar of silver clear of parting charges, the value of such silver is paid in sil- ver coin. The charges for refining and sepa- rating silver from gold vary from one cent to six cents an ounce ; for coinage of gold, one half of 1 per cent. ; and for making fine gold bars, six cents per $100 if the deposit contains silver, and if not, five cents an ounce. Deposits of silver are paid in silver. If the silver deposit contains the value of over one dollar in gold, clear of parting charges, the value of such gold is estimated and paid in gold coin. The charges for refining and separating gold from silver vary from one third of one cent to six cents an ounce; for coinage into trade dollars they are 50 cents per 100 pieces ; for making fine silver bars, one half cent an ounce on the fine silver. Silver bullion is purchased at 118 cents an ounce (standard fineness nine tenths pure sil- ver), and paid for in silver coin of less denom- ination than the dollar. Each deposit of gold or silver is melted and cast into bars, being thus brought into a homogeneous state, so that an assay piece taken from it shall fairly represent the mass. The assayer, operating upon a small quantity of the assay piece which he has taken, determines by an exceedingly delicate chemi- cal analysis the proportion of gold or silver or both which it contains. The fineness and the weight of the deposit after melting are the data for calculating its value. Deliveries of bullion, composed of these various deposits, are made from time to time to the melter and refiner, and are charged to him in account. It is his province to refine them, and convert them into ingots of standard metal, 900 thou- sandths fine, suitable for the fabrication of coins. Gold and silver in their pure state, on account of their softness, are altogether un- adapted for coin. Consequently, each metal is alloyed with a certain quantity of some other metal baser than itself, to give it greater hard- ness and durability. In the United States sil- ver, in the manufacture of silver coin, is alloyed with copper; the proportion in 1,000 being 900 parts silver and 100 parts copper; and in gold coin, 1,000 parts, 900 being pure gold, 100 alloy of silver and copper, of which not more than 50 parts is allowed by law to be of silver. In practice a very small fraction of this alloy FIG. 4. Rollers. is silver. By means of powerful but accurately constructed rollers, driven by steam, the ingots (which are bars sharpened at one end like the blade of a chisel, and about one foot long, three fourths of an inch to two and a half inches broad, and half an inch thick) are rolled into thin strips or ribbons of the proper thickness for the coin to be made, through the rollers exhibited in the drawing (fig. 4) just above the clock dial. This process is required to be gone through ten times for gold and eight times for silver. These strips must occasionally be an- nealed in furnaces, in order to soften them, before they are drawn, which latter operation is done by means of the drawing bench (fig. 5), in which they are drawn like wire through a steel gauge to make them straight and of uni- form thickness. Next comes the cutting press (fig. 6), a vertical steel punch working accu- rately into a matrix or round hole in a steel plate of the size of the planchet required, and operated rapidly by an eccentric, under which