324 ANNUAL OF SCIENTIFIC DISCOVERY. 



It is, finall.y, worthy of remark, that the mound-builders, as the Americans 

 call the race of the copper-age, seem to have immediately preceded and 

 prepared the way for the Mexican civilization, destroyed by the Spaniards; 

 for, in progressing southwards, a gradual transition is noticed from the 

 ancient earthworks of the Mississippi valley to the more modern construc- 

 tions of Mexico, as found by Cortez. 



In Europe the remains of a copper-age are wanting. Here and there a 

 solitary hatchet of pure copper is found. But this can be accounted for by 

 the greater frequency of copper, while tin had usually to be brought from a. 

 greater distance, so that its supply was more precarious. 



As Europe did not witness a regular development of a copper-age, it seems, 

 according to Mr. Troyon's very just remark, that the art of manufacturing 

 bronze was brought from another quarter of the world, where it had been 

 previously invented. It was most probably some region in Asia, producing 

 both copper and tin, where those two metals were first brought into artificial 

 combination, and where also traces of a still earlier copper-age are still likely 

 to be found. 



An apparently serious objection might be started here by raising the ques- 

 tion how mines could be worked without the aid of steel. This, however, is 

 sufficiently explained by the fact, that the hardest rocks can be easily man- 

 aged through the agency of fire. By lighting a large fire against a rock,, the 

 latter is rent and fissured, so as considerably to facilitate the quarrying. 

 This method was frequently employed when wood was cheaper, and is even 

 practised at the present day in the mines of the Rammelsberg in Germany, 

 where it facilitates the working of a rock of extreme hardness. 



That metal of dingy and sorry appearance, but more truly precious than 

 gold or the diamond, iron, at length appears, giving a wonderful impulse 

 to the progressive march of mankind, and characterizing the third great 

 phase in the development of European civilization, very properly called the 

 iron-age. 



Our planet never produces iron in its metallic or virgin state, for the 

 simple reason that it is too liable to oxidation. But among the aerolites 

 there are some composed of pure iron with a little nickel, which alters 

 neither the appearance nor sensibly the qualities of the metal. Thus the 

 celebrated meteoric iron discovered by Pallas in Siberia was found by the 

 neighboring blacksmiths to be malleable in a cold state. Meteoric iron has 

 even been worked by tribes to whom the use of common iron was unknown. 

 Thus Amerigo Vespucci speaks of savages near the mouth of the La Plata 

 who had manufactured arrow-heads with iron derived from an aerolite. 

 Such cases are certainly of rare occurrence, but they are not without their 

 importance, for they explain how man may probably first have become 

 acquainted with iron, and they also account for the occasional traces of iron 

 in tombs of the stone-age, if indeed this fact be well established. 



It is, notwithstanding, evident that the regular workings of terrestrial 

 iron-ore must have been a necessary condition of the commencement and 

 progress of the iron-age. 



Now, iron-ore is widely diffused in most countries, but it has usually the 

 look of common stones, being distinguished more by its weight than iis 

 color. Moreover, its smelting requires a much greater degree of heat than 

 copper or tin, and this renders its production considerably more difficult 

 than that of bronze. 



But, even when iron had been obtained, what groping in the dark and 



