Do geologists use radiometric dating
One referred to the depth of the sediments and the time they would have taken to accumulate; the other referred to the salinity of the oceans, compared with the rate at which rivers are supplying them with sodium salts.
In hindsight, both theories were deeply misguided, for similar reasons.
Nevertheless, by the late 19th century the geologists included here had reached a consensus for the age of the earth of around 100 million years.
Having come that far, they were initially quite reluctant to accept a further expansion of the geologic timescale by a factor of 10 or more.
It is a drama consisting of a prologue and three acts, complex characters, and no clear heroes or villains.
We, of course, know the final outcome, but we should not let that influence our appreciation of the story as it unfolds.
Roman poet Lucretius, intellectual heir to the Greek atomists, believed its formation must have been relatively recent, given that there were no records going back beyond the Trojan War.
The Talmudic rabbis, Martin Luther and others used the biblical account to extrapolate back from known history and came up with rather similar estimates for when the earth came into being.
The second depended on highly dubious theories of formation of the earth and moon and plays relatively little role in this compilation.
They assumed that current rates—of sediment deposition and of salt transport by rivers—were the same as historical rates, despite the evidence they had that our own age is one of atypically high geologic activity. The rock cycle, as we now know, is driven by plate tectonics, with sedimentary material vanishing into subduction zones.
And the oceans have long since approached something close to a steady state, with chemical sediments removing dissolved minerals as fast as they arrive.
The second referred to such topics as the detailed shape of the earth (bulging slightly at the equator) and the dynamics of the earth-moon system.
The third referred to the heat of the sun, particularly the rate at which such heat is being lost, compared with the total amount of energy initially available.
Florian Cajori, author of the 1908 article “The Age of the Sun and the Earth,” was a historian of science and, especially, of mathematics, and Ray Lankester, whom he quotes, was a zoologist. The first act consists in a direct attack, led by Lord Kelvin, on the extreme uniformitarianism of those such as Charles Lyell, who regarded the earth as indefinitely old and who, with great foresight (or great naivety, depending on your point of view: see the third installment of the 1900 “The Age of the Earth” article by W. Sollas), assumed that physical processes would eventually be discovered to power the great engine of erosion and uplift.