Bronze, as every one knows, is an alloy of copper and tin (nine parts of copper and one of tin). Now it is precisely this alloy, namely bronze, which was the first metallic substance used in Europe; indeed the sole substance used, to the exclusion of copper. We have, therefore, to explain the somewhat singular circumstance that an alloy and not a pure metal was the metallic substance that was earliest used in Europe; and we must also inquire how it was that bronze could have been composed by the nations which succeeded those of the polished-stone epoch. At first sight, it might appear strange that an alloy like bronze should have been the first metallic substance used by man, thus setting aside iron, deposits of which are very plentiful in Europe. But it is to be remarked, in the first place, that iron ores do not attract the attention so much as those of tin and copper. Added to this, the extraction of iron from its ores is one of the most difficult operations of the kind. When dealing with ferruginous ores, the first operation produces nothing more than rough cast iron--a very impure substance, which is so short and brittle that it possesses scarcely any metallic qualities, and differs but little from stone as regards any use it could be applied to. It requires re-heating and hammering to bring it into the condition of malleable iron. On the other hand, by simply smelting together copper and tin ores and adding a little charcoal, bronze might be at once produced, without any necessity for previously extracting and obtaining pure copper and tin in a separate state. This will explain how it came to pass that the earliest metal-workers produced bronze at one operation, without even being acquainted with the separate metals which enter into its composition. We are left entirely to hypothesis in endeavouring to realise to ourselves how men were led to mix together copper and tin ores, and thus to produce bronze--a hard, durable and fusible alloy, and consequently well adapted, without much trouble, for the fabrication, by melting in moulds, of hatchets, poniards, and swords, as well as agricultural and mechanical instruments. Bronze was endowed with all the most admirable qualities for aiding the nascent industrial skill of mankind. It is more fusible than copper and is also harder than this metal; indeed, in the latter respect, it may compete with iron. It is a curious fact that bronze has the peculiarity of hardening when cooled gradually. If it is made red-hot in the fire and is then suddenly cooled by plunging it into water, the metal becomes more ductile and may be easily hammered; but it regains its original hardness if it is again heated red-hot and then allowed to cool slowly. This, as we see, is just the contrary to the properties of steel.