The next step in the conversion of bullion into coin is the assembling of the refined metal into "'melts" of about 3,000 ounces to which sufficient copper is added to render the melted mass 900 parts fine, which is the standard fine ness of United States gold and silver coin. When melted the metal is cast into ingots of the size proper for the production of the coin required. This alloy is rigidly tested by assay, and if found standard within the legal tolerance it is so declared, and the ingots are delivered to the coiner for conversion into coin. They are first taken to the rolls, "broken down," annealed and delivered at the finishing rolls, where they are converted into coin strips of the requisite thickness for coin blanks. The strips are then talcen to the cutting machines, where they are converted into coin blanks which go to the se lecting tables for the elimination of imperfect pieces and fragments. The accepted blanks are then sent to the adjusting room, where, if gold, each piece is weighed, the heavy pieces being reduced by filing and brought within the limit of legal tolerance. If the blanks be silver they are passed through automatic selecting machines which separate them into standards, heavies, lights, within tolerance and condemned lights. The blanks are next passed into a machine and "upset," or "milled," which process so raises the edge of the piece as to protect the work on the stamped coin from abrasion. The blanks are then annealed, treated to a dilute sul phuric acid bath and cleansed and brightened, and when thoroughly dried are ready for the coining-presses. These presses work automatic ally, the only hand action being to fill the feed ing tubes. The pieces are automatically seized by conveyers and centred between the obverse and reverse dies within a collar a little exceed ing the piece in diameter. The impact of the dies, brought together by the operation of a toggle joint, forces the metal to flow to the full diameter of the collar, which is grooved inside, and puts a fine reeding upon the edge of the coin. The finished coin is then auto matically passed on and is followed by others, the delivery for large coins being at the rate of 80 or 90 per minute. Dimes are stntck at the rate of 100 and 120 per minute.
The standard, heavy and light coins are then separately counted by gauge and made into drafts of $5,000 each, if gold, and drafts of $1,000 each, if silver. As the standard weight of gold drafts of $5,000 is 268.75 troy ounces, the standard, heavy and light coins are mingled in due proportion to make that standard weight, no greater variation than one one-hundredths of an ounce being allowed. The standard weight of $1,000 in silver dollars is 859.375 ounces and of subsidiary silver 803.75 ounces, with a tolerance of two one-hundredths of an ounce. The perfected drafts are then weighed in the presence of the superin tendent, enclosed in canvas bags and delivered to that officer. The mint balances are adjusted to the troy pound (5,760 grains) which is the mint unit of weight. This weight is a dupli cate of the troy pound established by a royal commission in England in 1758, reaffirmed in 1838. It is kept ill a special safe at the Phila delphia mint. In order to secure an exact con formity in weight and fineness of United States coin, a fixed number of coins is taken from every delivery, sealed in the presence of the superintendent and the assayer, and deposited in a receptacle called "the pyx," each of those officers having a key. both keys being required to open the pyx. These reserved pieces al,vait the assembling of the Assay Commission, an nually appointed by the President to meet on the second Wednesday in February, when the pyx is opened and exhaustive tests of the weight and fineness of the contents are made.
Location and Equipment. — The principal mint of the United States is located on Spnitg Garden street, between 16th and 17th streets, Philadelphia. Other mints are at New Or leans, San Francisco and Denver. The equip ment of the Philadelphia mint, which covers 58,000 square feet, consists of eight boilers of 1,200 horse-power capacity, for heating, venti lating and electric lighting. To avoid the trans fer of power by shafting the machinery is chiefly operated by independent motors. The
building is lighted by 4,000 incandescent and 16 arc lights. There are 51 telephones connecting the departments and various offices. A gas plant, capable of delivering upward of 20,000 cubic feet per hour, furnishes fuel for the melt ing, annealing and assaying furnaces. Thc ven tilating is.by fans operated by attached motors. The spacious melting department is equipped with 13 gas and 3 coal heated furnaces, with power topping machines. The coining depart ment has 23 coining-presses with an average capacity of 110 pieces of finished coin, each, per minute; 10 milling or upsetting machines, each capable of an out-turn of an average of 500 milled blanks per minute; a full equipment of trains of break-down and finishing rolls; 8 strip annealing gas furnaces and 1 furnace for an nealing blanks; 8 automatic presses for cut ting blanks from coin strips; 6 automatic weighing machines for the separation of blanks into standard, heavy, light and con demned pieces, together with appliances for cleaning, whitening and drying blanks after an nealing. The assaying department is equipped with every known appliance for determining the fineness of gold and silver, both by the plat inum and the humid processes. The refinery operates largely the acid process of separating, but it has a plant for refining by electrolysis and the process has 'proved a success, consider ably increasing the capacity of the refinery.
The engraving department provides all of the coin dies used in the mints of the United States. It has every facility for die-sinlcing, hubbing and annealing the steel from which dies arc produced, as well as a geometric lathe for transferring designs. The department for the manufacture of medals of a national char acter is in charge of the engraver, who pro vides the dies. The medal departinent is equipped with three hydraulic presses of the re spective capacity for exerting a pressure of 1,100, 400 and 300 tons. These powerful presses are operated by electric motors. The machine shop has every appliance for the construction or the assembling and finishing of all machinery used in the mint. There are 20 steel-lined vaults for the storage of coin and bullion and for the use of the operative officers. One of these vaults has a floor-space of 5,200 square feet, with a storage capacity of 112,000,000 sil ver dollars. Another has a floor-space of 4,160 square feet. Six others have each a floor-space of 2,562 square feet. The basement vaults are built wholly independent of the en closing walls, with a free passageway around them. The doors are massive and provided with the finest locks procurable. to which time locics are attached. More than 3,250,000 pounds of steel enter into the construction of these vaults. The vestibule is highly ornate, the cor ridor extending through the cross-section from east to west is finished in richly variegated marble and the main staircase is of white mar ble. The floors are of messanine, the symbolic panels in the vestibule of glass mosaic. The ceilings are finished in white and gold.
The cabinet, or museum, is in a specious room at the head of the main staircase in the rotunda. It contains a fine collection of the coins of all nations, ancient and modern, a full line of medals of a national character and many rare medals of foreign countries. There is also a fine collection of curios, many of them col lected in distant lands. The working capacity of the mint considerably exceeds the national demand 'for its product. Congress has there fore authorized coinage for other nations at a fair remuneration. Pursuant to this authoriza tion the mint has coined much gold and silver, as well as copper and nickel coin, for several of the South American and most of the Central American states. Prior to the annexation, the mint at San Francisco coined money for the Sandwich Islands. Admission to the mint is free to the public on every worlcing day between the hours of 9 A.m. and 2 P.M. The building is patroled day and night by an armed guard.
See BANKS AND BANKING ; BULLION ; COINAGE ; COINS, FOREIGN, Am ERICA N EQUIVALENT OF ; CURRENCY ; DOLLAR ; GOLD; GOLD STANDARD AND PRODUCTION ; GOLD STANDARD BILL ; LEGAL TENDER ; MINT ; MONEY ; NUMISMATICS ; SILVER.