COINS 223 In all annealing of strips in the wood-fire fur naces the strips were superposed unavoidably, and it was not always easy to determine when the draft reached a uniform cherry-redness. Delays and refractory metal were common with the old method of anneali,pg. Besides, the method was the reverse of economical, owing to oxidation of the metal.
In substituting the gas annealing furnace for the wood-fire furnace the work of rolling the metal soon became a work of precision. A considerable saving of time was also effected. The gas annealing furnace for strips has a heating chamber 10 feet in length, 17% inches in width and 10 inches in depth. A score of hol low rolls, named mounted on hol low shafts of cast-iron, are so ribbed as to di vide the face into several parts conformed to the width of the strips. These ribs separate the strips and prevent superposition. The gas burn ers enter the heating chamber at the bottom and are in sections, in order to secure independ ent control. Through these burners a mixture of gas and air is injected along the whole length of the chamber. The strips to be annealed are placed on the rolls at the entrance of the furnace, the rolls are rotated by worm wheels and pass entirely through the chamber, to enter a hood at the discharge end of the furnace. In this hood the strips, now of a cherry-red, are met by a flame surcharged with gas to prevent oxidation. A spray of water is applied to the strips outside the hood to cool them before they reach the air. This prevents the oxidation of the copper with which the metal is alloyed. The process thus described occupies about six minutes, instead of the hour, or even more, by the wood-fire furnaces. The time required in annealing silver is about 20 or 25 minutes as to the larger denominations. Dimes, however, not being adjusted, and the coin strip being pro duced from the dollar ingot, require a more prolonged annealing. The improvement in an nealing has made it possible to produce from the ingot strips as high as 83 to 96 per cent of standard blanks and blanks within the limit of tolerance, suitable for coining. This high per centage of good blanks is undoubtedly due to improved annealing and rolling. It is a higher percentage than has ever been secured when the defects in annealing and rolling were in part remedied by the draw-bench. As that ma
chine is still employed in mints not strictly up to date, it may not be amiss to say, that in principle the draw-bench is a wire-drawing ma chine. As under the old mode of developing the ingot into the strip the ductility of the strip was not uniform, some parts being more refractory than others, and hence not reduced to a uniform thickness by the rolls, it was found necessary to pass the strips through a rigid die. The strips were then pointed so as to be firmly gripped by the nippers of the draw-bench which, retreating, drew the strip through the rigid die and gave it a uniform thickness, now imparted by rolls of precision without wasteful annealing. This improvement not only works a reduction of waste, but saves a delay between the finish ing rolls and the cutting presses.
The largest gold pieces ever coined by the United States government are the 600 $50 pieces coined as mementoes of the Panama-Pacific In ternational Exposition. Up to 30 June 1915, the gold coinage of the United States was, in nutnber of coins: Double eagles ($20) 120,757,306; eagles ($10) 51,122,910; half eagles ($5) 77,421,791; quarter eagles ($2.50) 17,260,490; $3 pieces 539,792; $1 (gold) 19,814,837. The silver coin age totals: Standard dollars 578,303,848; trade dollars 35,965,924; standard half dollars 379, 768,022; Columbian and other souvenir half dol lars 5,110,000; quarter dollars 410,991,308; 20 cent pieces 1,355,000; dimes 733,837,547; half dimes 97,604,388; 3-cent pieces 42,736,240; nickels 855,008,587. A 3-cent nickel piece and a 2-cent bronze piece have also been coined and a half-cent of copper. The cent has been coined in copper, nickel and for many years in bronze to the total of about 2,700,000,000. The total coinage of the country is in dollars $4,439,067, 448.35. The principal foreign coins and their value in United States gold are: English, the sovereign or pound sterling, $4.86; French and Swiss franc, $0.19; German mark, $023; Rus sian ruble, $Q.51; Italian lira, $0.19; Swedish and Denmarlc crown, $027; Netherlands florin, Spanish peseta, $0.19; Argentine peso, .96; Brazilian milreis, $0.55; Chilean peso, .36; Japanese yen, $0.50; Indian rupee, $0.32. e COIN and its cross-references. Consult 'Coinage Laws of the United Hepburn, of Coinage and Currency in the United (New York 1903).