The Richard Dixon Oldham reference article from the English Wikipedia on 24-Jul-2004
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Richard Dixon Oldham

Helping orphans the way you would do it
Richard Dixon Oldham (July 31, 1858 - July 15, 1936) was a British geologist who, in 1906, argued that the Earth must have a molten interior as S waves were not able to travel through liquids nor through the Earth's interior.

See also: Lehmann, Inge, seismology