Our Physical World a Source book of Physical Nature Study
The book Our Physical World a Source book of Physical Nature Study was written by author Elliot Rowland Downing Here you can read free online of Our Physical World a Source book of Physical Nature Study book, rate and share your impressions in comments. If you don't know what to write, just answer the question: Why is Our Physical World a Source book of Physical Nature Study a good or bad book?
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That was so very long ago we do not know what his methods were. But following the man of the chipped-stone age and of the polished-stone age, there came peoples who made bronze utensils, and that time is known as the Bronze Age. Bronze is made by melting together tin and copper. So those people must have know how to extract tin from its ores. We know the tin mines of Cornwall, England, were worked during Roman times and probably very much earlier. Then came the age of iron implements. Some sava...ge tribes have today very crude processes for extracting iron from its ore. FIRE AND ITS USES 159 Possibly the process was discovered when some savage used an easily reduced ore of iron like siderite (see p. 50) to build a fire- place, and found after many fires a bit of iron in it that could be hammered out into serviceable shape. At any rate, the iron forge among some African and Asiatic tribes is today simply a hole dug in a high clay bank to serve as a fireplace in which a charcoal fire is built and bits of iron ore and limestone are added, then more charcoal, limestone, and iron ore, layer after layer.
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