GEOLOGY. 323 



melts and moulds well; the molten mass in cooling slowly acquires a tolera- 

 ble degree of hardness, inferior to that of steel, it is true, but superior to that 

 of very pure iron. We therefore understand how bronze would long be used 

 for manufacturing cutting-instruments, weapons, and numerous personal 

 ornaments. The northern antiquaries have very properly called this second 

 great phase in the development of European civilization the bronze-age. 



The bronze articles of this period, with a few trifling exceptions, have not 

 been produced by hammering, but have been regularly cast, often with a 

 considerable degree of skill. Even the sword-blades were cast, and the 

 hammer (of stone) was only used to impart a greater degree of hardness to 

 the edge of the weapon. 



The bronze age has therefore witnessed a mining industry, which was 

 completely wanting during the stone-age. Now the art of mining is so 

 essential to civilization, that without it the world would perhaps yet be 

 exclusively inhabited by savages. It is then worth our while to inquire 

 more closely into the origin of bronze. 



Copper was not difficult to obtain. In the first place, virgin copper is not 

 particularly scarce. Then, the different kinds of ore which contain copper 

 combined with other elements are either highly colored, or present a marked 

 metallic appearance, and are consequently easily known; they are besides 

 not hard to smelt, so as to separate the metal. Finally, copper ore is not 

 at all scarce; it is met with in the older geological series of most countries. 



Virgin tin is unknown, but tin ore is heavy, of dark color, and very easy 

 to smelt. However frequent copper may be, tin is of rare occurrence. Thus 

 the only mines in Europe which produce tin at the present day are those of 

 Cornwall in England, and of the Erzgebirge and Fitchtelgebirge in Germany. 



But the question arises whether, previous to the discovery of bronze, man, 

 owing to the great rarity of tin, may not have begun by using copper in a 

 pure state. If so, there would have been a copper-age between the stone-age 

 and the bronze-age. 



In America this has been really the case. When discovered by the Span- 

 iards, both the two centres of civilization, Mexico and Peru, had bronze, 

 composed of copper and tin, and used it for manufacturing arms and 

 cutting-instruments in the absence of iron and steel, which were unknown in 

 the New World. But the admirable researches of Messrs. Squier and Davis 

 in the antiquities of the Mississippi valley have brought to light an ancient 

 civilization of a remarkable nature, and distinguished by the use of raw 

 virgin copper, worked in a cold state, by hammering, without the aid of fire. 

 The reason of its being so worked lies in the nature of pure copper, which 

 when melted flows sluggishly and is not very fit for casting. A peculiar 

 characteristic of the metal, that of occasionally containing crystals of virgin 

 silver, betrays its origin, and shows that it was brought from the neighbor- 

 hood of Lake Superior. This region is still rich in metallic copper, of which 

 single blocks attaining a weight of fifty tons have lately been discovered. 

 There was even found at the bottom of an old mine a great mass of copper 

 which the ancients had evidently been unable to raise, and which they had 

 abandoned, after having cut off the projecting parts with stone hatchets. 



The date of that American copper-age is unknown. All we know is, that 

 it must reach at least as far back as ten centuries, that space of time being 

 deemed necessary for the growth of the virgin forests now flourishing upon 

 the remains of this antique civilization, of which the modern Indians have 

 not even retained a tradition. 



