The Project Gutenberg Ebook Of The Economic Aspects Of
In making up this table it is assumed that the rocks to a depth of ten miles are about 95 per cent of igneous type that is crystallized from molten magma and about 5 per cent of sedimentary type that is formed from the weathering and erosion of igneous rocks or prexisting sediments and deposited in beds or layers either by water or by air see pp 1617
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