Radioactive dating assumptions
He was one of the dominant physicists of his time, the Age of Steam.
His achievements ran from helping formulate the laws of thermodynamics to advising on the first transatlantic telegraph cable. Shelton was a philosopher of science, critical (as shown in his contribution, the 1915 article “Sea-Salt and Geologic Time”) of loose thinking and a defender of evolution in debates.
In hindsight, both theories were deeply misguided, for similar reasons.
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.
Robert Hooke, not long after, suggested that the fossil record would form the basis for a chronology that would “far antedate ...
even the very pyramids.” The 18th century saw the spread of canal building, which led to the discovery of strata correlated over great distances, and James Hutton’s recognition that unconformities between successive layers implied that deposition had been interrupted by enormously long periods of tilt and erosion.
And the oceans have long since approached something close to a steady state, with chemical sediments removing dissolved minerals as fast as they arrive.
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.
This position came to be known as uniformitarianism, but within it we must distinguish between uniformity of natural law (which nearly all of us would accept) and the increasingly questionable assumptions of uniformity of process, uniformity of rate and uniformity of outcome.That is the background to the intellectual drama being played out in this series of papers.