“I venture to suggest that somehow”: Kelvin 1904.

In 1904, however, with considerable: Physicist and Nobel laureate Sir Joseph John “J. J.” Thomson (not related to Lord Kelvin), who discovered the electron, reminisced in 1936 that Kelvin acknowledged in a conversation that the discovery of radioactive heating undermined his assumptions in the calculation of the Earth’s age; Thomson 1936, p. 420. Kelvin made a similar concession during the British Association meeting; Eve 1939, p. 109.

In an acerbic exchange: It started with a letter by Kelvin, published on August 9, 1906, in which he repeated his belief that the Sun’s energy was only gravitational and asserted that radioactivity was no more than a hypothesis. Various rebuttal letters by Frederick Soddy, Oliver Lodge, Robert John Strutt (physicist and son of Lord Rayleigh), and Kelvin appeared for about a month. In his letter of August 15, Lodge said about Kelvin that “his brilliantly original mind has not always submitted patiently to the task of assimilating the work of others by the process of reading.” The episode is described briefly in Eve 1939, pp. 140–41, Burchfield 1990, p. 165, and Lindley 2004, p. 303. A review of the controversy is in Soddy 1906.

I came into the room: Cited, eg, in Eve 1939, p. 107.

Eventually, radiometric dating: Holmes 1947 gives a nice review. Today’s accepted age was first determined by geochemist Clair Patterson by using data from the Canyon Diablo meteorite (Patterson 1956). Scientists at Argonne National Laboratory have put radiometric dating to another interesting use. Using the decay of the rare isotope krypton 81, they succeeded in 2011 in tracking the ancient Nubian Aquifer that stretches across northern Africa.