METALLURGY 



149 



Ancient Metallurgy. From an ethnological point 

 of view one of the most interesting questions con- 

 nected with the origin of the industrial arts is when, 

 and under what circumstances, man first liegan to 

 we irk metals by softening or melting them liy means 

 of a high heat. The art of smelting ores was prob- 

 ably discovered by observing the effect of a big fire 

 on some rich ore that happened to be in the way. 

 Gold is always found native, and silver and copper 

 snniftinies. The ancient Egyptians worked in gold, 

 silver, and bronze with a degree of skill that could 

 only have been reached by gradual steps extending 

 over thousands of years. In the notes to his edition 

 of WiUeauettt Ancient Egyptians, Dr Birch says 

 that it U uncertain whether metallic tin was known 

 to them, as Bronze (q.v. ) may have been made by 

 the use of tin ore along with copper. He also states 

 that the question of the use of iron among them has 

 been rendered doubtful by the few specimens of that 

 metal found in the monuments and sepulchres. 

 Some examples, however, have been met with, 

 although only in one case apparently is the approx- 

 imate age of the object known. It is iron wire in 

 a bronze statue of the time of the Kamesidg. In 

 India anil some other parts of Asia malleable iron 

 U made directly from rich ores in furnaces scarcely 

 bigger than chimney -cans, by a process in use from 

 11 mi- immemorial ; and by a similar process savages 

 in some parts of Africa also smelt iron. It is sup- 

 I H i -ed I >v .-nine archaeologists that most parts of 

 Africa passed directly from the stone to the iron 

 age, but there seems to lie evidence that in some 

 places on that continent the making of various 

 articles of the copper of the country has been long 

 practised by aboriginal tribes. 



Among the remains found in the lake-dwellings 

 of central Europe are crucibles for melting metals, 

 ingots of copper and tin, and in one crucible traces 

 of gold were found. Bronze implements are abund- 

 ant, but the considerable number of copper hatchets 

 which have now Iwcn discovered has raised the 

 question as to whether in prehistoric times a copper 

 age has not preceded those of bronze and iron Copper 

 is more easily smelted than iron ; and bronze, being 

 an alloy of copper and tin, must mmewhen have 

 been preceded in its application to hatchets or other 

 articles by unalloyed copper, although this may not 

 have been the case in Euro|>e. Some copper 

 hatcheta, and other implements of this metal, are 

 the only evidence we have that the ancient 

 Mexicans made any use of metal tools : though 

 their artificers were skilled in casting gold and 

 silver, and in hammered work and chasing, and tin 

 as well as copper ore was mined, ami the two 

 combined as bronze. The early tribes inhabiting 

 the country about Lake Su|>erior, where native 

 copper is plentifully found, made knives and orna- 

 ments of the metaf by hammering it cold, in some 

 cases, it is believed, with stone implements. Small 

 chisels, rings, idols, and other objects made of 

 gold and of ancient date, some of winch are of thin, 

 flat beaten plates, have been obtained in the re- 

 pulilic of Colombia, South America. Silver articles 

 of a rude archaic character appear to 1 rare. It 

 in likely that the working of these native metals in 

 the cold state in certain limited areas preceded the 

 art of manipulating any metal by heat. 



See Liilibock'i Prehistoric Timtt, Munro's Lake-dwrll- 

 iii//j of Europe, NatiaiUac's Prehistoric America, and 

 various paper* in the volumes of Contribution* t Know- 

 ledge published by the .Smithsonian Institution. 



Modern Metalhtrr/y. As now understood this is 

 the art of extracting metals from their ores. The 

 operations are partly mechanical and partly chem- 

 ical. Those processes which depend principally on 

 chemical reactions for their results have reference 

 chiefly to the roasting and smelting of ores, and 

 are described under the heads of the different metals. 



But there are certain preliminary operations of a 

 mechanical kind which metallic ores undergo, such 

 as crushing, jigging, washing, &c. , which we shall 

 describe here, as they are essentially the same for 

 the ores of lead, copper, tin, zinc, and indeed most 

 of the metals. Until comparatively recent times 

 ore, or rather ore-gangue, as it came from the mine 

 was in the first instance broken by hammers before 

 being passed on to crushing-rollers or stamps to be 

 reduced to smaller pieces or grains. In the year 

 18o8 Mr E. W. Blake of New Haven, Connecticut, 

 invented a stone or ore crusher which has become 

 so extensively used that it has, except in special 

 cases, superseded hand-labour for breaking up large 

 pieces of ore. Fig. 1 shows in section a modifica- 

 tion of Blake's ore-crusher, made by Marsden of 



Fig. 1. 



Leeds. The shaded portion shows the fixed jaw, 

 A, and the movable jaw, B, between which the 

 ore or stone is crushed. To the movable jaw a 

 rapid biting movement (reaching 250 strokes per 

 minute) is given by means of an eccentric lever 

 and toggle-joints. C is the rod connecting the 

 eccentric with the toggle-plates, DD. The machine 

 is driven by a shaft and pulley, and has a balance- 

 wheel. A spring or lever near the base of the 

 machine aids the return movement of the jaw, B. 



The vein-stuff or impure ore is next taken either 

 to the crushing-rollers or to the stamping-mill. 

 Fig. 2 shows a section of a crushing-mill of German 



I'l | ^'pfe<yg|-.'bF| Pjl 

 \\ i i ^ ...y; /...r~g 

 VA v teart r A? 



Fig. 2. Ore-crushing Mill : 

 End view of the crushing-rollers, sieves, and bucket-wheel. 



design, but nearly resembling that in use in Corn- 

 wall for treating copper, lead, and zinc ores. The 

 ore, already reduced by the Blake jaw-crusher to 



