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More than 5000 entries on the history, culture and life of Britain (published in 1993 by Macmillan, now out of print)
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geological periods
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In the 1830s there was a concentrated effort in Britain to identify the correct sequence of early fossil-bearing rock strata (the work of James *Hutton in the previous century had opened the door to this kind of scientific approach). Two great geologists were in the vanguard, sometimes complimenting each other's work and sometimes clashing. Adam Sedgwick (1785–1873) began investigating the rocks of north Wales in 1831 and gave the name Cambrian (from Cambria, new Latin for Wales) to what he considered the oldest fossil-bearing stratum. In the same year Roderick Murchison (1792–1871) began work in the border districts of south Wales; he identified a more recent group of strata which he called Silurian (from the Silures, a Celtic tribe so named by the Romans).
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The friendship between Sedgwick and Murchison at this period was evident when they together identified and named, in 1839, the Devonian period – more recent again, and seen in the rocks of south Devon. Their famous dispute came later, over where the dividing line lay between their respective Cambrian and Silurian periods. It was not resolved until 1879, after both their deaths, when Charles Lapworth (1842–1920) proposed an intermediate period which he called Ordovician (from the Ordovices, another Welsh tribe). Subsequently the *geological periods have been dated and named in a full sequence, from the Palaeozoic era through the Mesozoic and Cenozoic to the present day.
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