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Most notable is William Thomson, ennobled to become Lord Kelvin in 1892, whose theories make up an entire section of this collection.He was one of the dominant physicists of his time, the Age of Steam.Lord Kelvin and his allies used three kinds of argument.The first of these referred to the rate of heat loss from the earth and the length of time it would have taken to form its solid crust.The most famous came in 1654, when Archbishop James Ussher of Ireland offered the date of 4004 B. Within decades observation began overtaking such thinking.In the 1660s Nicolas Steno formulated our modern concepts of deposition of horizontal strata.
That is the background to the intellectual drama being played out in this series of papers.The first argument was completely undermined after taking into account the amount of heat generated by radioactive decay.The second depended on highly dubious theories of formation of the earth and moon and plays relatively little role in this compilation.It was not until 1926, when (under the influence of Arthur Holmes, whose name recurs throughout this story) the National Academy of Sciences adopted the radiometric timescale, that we can regard the controversy as finally resolved.Critical to this resolution were improved methods of dating, which incorporated advances in mass spectrometry, sampling and laser heating.
Even less should we let that knowledge influence our judgment of the players, acting as they did in their own time, constrained by the concepts and data then available.