130 



THE MINTS OF THE UNITED STATES. 



[1855. 



livered as coin in fourteen days after its arrival, and the third- 

 third in eighteen days. 



But as there is a bullion-fund of §5,500,000 allowed by 

 government, depositors are paid from the third to the fifth day 

 after an arrival, i.e., as soon as the gold is melted, assayed, 

 and its value calculated. When two heavy arrivals occur in 

 close succession, the time of refining and coining can be short- 

 ened from 14 to 10 days. 



The number of men engaged in the refining department is 

 14 : 1 foreman, 8 for the parting process, 3 for reducing, and 

 2 for pressing and drying. In the gold melting-room there 

 are o melters and 2 assistants. The total number of hands in 

 the melting and refining departments is 34, including a melt- 

 ing and parting foreman, and 3 in the place for grinding, sifting, 

 washing, and sweeping. This last place or sweep embraces all 

 pots, ashes or fires, trimmings of furnaces, ashes of all wood- 

 work, &e. 



The late law for reducing the weight of silver coin 

 necessitated an increase of force, and 15 more were in conse- 

 quence employed for this purpose. While $50,000,000 in a 

 year have been parted with the above force, they could with 

 the same force and apparatus refine §80,000,0000 if it were 

 required. 



After many experiments upon anthracite. Professor Booth 

 stated that he had at length fully succeeded in employing it 

 for melting both gold and silver in the same furnaces, slightly 

 modified, in which he had been accustomed to melt with char- 

 coal. This change had been accompanied by great economy 

 in the cost of material and labour, and by greater comfort to 

 the workmen, from being less exposed to heat. The cost of 

 charcoal (of the best quality — hard pine-knot coal) is 16 cents 

 per bushel, delivered at the Mint ; and while the cost of this 

 fuel for aU their operations in 1852, when gold was chiefly 

 refined and melted, was about S7000, the cost of anthracite 

 will be from 6600 to 61000. In using the anthracite he found 

 that a simple draught of air, without a blast, was quite suflEicient 

 to sustain combustion. 



Califomian gold frequently contains the alloy " iridosmine," 

 which is not always detected by the assay. In order to remove 

 it as far as possible without actually dissolving gold, it is al- 

 lowed to subside, first in the granulating crucibles, and then in 

 the crucibles for toughening (melting fine gold and copper). 

 If the assayers report its presence in the toughened bars, they 

 are again melted, and the iridosmine allowed to subside. By 

 these three, and often four successive meltings, the gold is 

 separated from its troublesome companion as far as practicable. 

 The gold thus refined, and reduced to the proper standard 

 [^Section 8 : " And be it further enacted, that the standard for 

 both gold and silver coins for the United States shall hereafter 

 be such that of 1000 parts by weight 900 shall be of pure 

 metal and 100 of alloy ; and the alloy of silver coins shall be 

 of copper, and the alloy of gold coins shall be of copper and 

 silver, pro\'ided that the silver do not exceed one-half of the 

 whole alloy,"] is delivered over to the chief coiner in the form 

 of bars or ingots of a certain weight, to be divided and shaped 

 into pieces required for the currency of the counti-y. 



The Coining department of the establishment is of a power 

 and efficiency sufiicient to perform all the mechanical processes 

 incidental to the issue of nearly 70,000,000 of pieces during 

 the past year ; and I was assured by Mr. Franklin Peale, the 

 chief coiner, that it could have executed much more if it had 

 been steadily employed, or fully supplied with material during 



the whole of that period. It is not necessary to go through 

 the whole course of operations in this department, but to notice 

 only such as possess novelty or present special characteristics. 



The necessary power for working the machinery is obtained 

 from a large steam-engine of the form usually known as the 

 steeple-engine ; it is a double vertical high-pressure engine, 

 with cranks at right angles, the power being carried off by a 

 caoutchouc belt, 2 feet wide, from a drum of 8 feet in 

 diameter ; the estimated power is equal to 90 horses. At times, 

 this is all required, at others much less is sufficient, and in un- 

 certain proportions ; to meet this irregularity, and to insure 

 that steadiness of motion so necessary in such delicate oper- 

 ations, a governor and throttle-valve of a peculiar construction 

 have been devised which have now been in use for some time, 

 and have produced most satisfactoiy results, iully eflFecting the 

 purpose for which they were designed. The rolling mills, four 

 in number, are driven by belts, at the rate of six revolutions 

 per minute ; the distances between the rollers being adjusted 

 by double wedges, moved by a train of wheels which are con- 

 nected with a dial-plate and bands, divided and numbered into 

 hours and minutes, so as to indicate the proper thickness of 

 the stripes of metal without the use of gauges. Gold stripes 

 are heated in an iron heater by steam, and waxed with a cloth 

 dipped in melted wax, and the silver strips are coated with 

 tallow by means of a brush. The draw bench is used for both 

 metals, and trial pieces are cut from every strip and their 

 weight tested, preparatory to the cutting of the whole. 



The cutting processes are very simple and eflncient, consis- 

 ting of a shaft moved by pulleys, and a 22-inch belt, with a fly- 

 wheel of small diameter but sufficient in momentum to drive 

 the punch through the slip of metal by means of an eccentric 

 of 1-inch, at the rate of 250 pieces per minute, which skilled 

 hands can readily accomplish and continue until the slip is 

 exhausted. The annealing during the rolling of the ingots 

 into slips is performed in copper cases, in muflles of fire-clay 

 and brick, heated by anthracite coal, three muffles or hearths 

 being kept at a bright red heat by one fire-grate or furnace, 

 and the distribution and intensity regulated by dampers. These 

 annealing furnaces are recent in their construction and very 

 satisfactory in operation ; they are heated by anthracite at the 

 cost of about one-fourth the expense of the wood previously 

 employed. 



The whitening of planchets is performed as usually by in- 

 closing the gold in luted boxes, and by exposing the silver in 

 an open pan, to the heat of a simple furnace with wood fuel ; 

 the drying and sifting after the action of dilute sulphuric acid, 

 is rapidly and effectually accomplished by a rolling screen — 

 one portion of which consisting of a pair of closed concentric 

 cylinders, between which high-pressure steam is admitted. 

 The blanks, with a sufficient quantity of light wood sawdust 

 (linden or bass wood is the best), being introduced into the in- 

 terior cylinder, a revolving motion is given to it by the engine 

 for a certain time ; the door is then opened and the blanks and 

 sawdust gradually find their way into the wire screen by which 

 they are separated, the movement being continued until the 

 separation is complete, when the blanks are discharged at the 

 end of the machine. An arrangement exists by which a 

 slight inclination is given to the machine so as to direct the 

 motion of the blanks towards the discharging end. 



The milling machines are, I was informed, peculiar to this 

 mint, and are in a great measure original, the operation being 

 performed by a continuous rotary motion, with great rapidity 



