Suspected that Earth was then much older. 1897 Quantitative Scientific Methods Lord Kelvin assumed that the Earth was originally molten and calculated a date based on cooling through conduction and radiation. Age of Earth was calculated to be about 24-40 million years. John Joly calculated the rate of delivery of salt to the ocean. River water has only a small concentration of salts.
Rivers flow to the sea.
Evaporative concentration of salts. Age of Earth was calculated to be 90-100 million years. Principles of Radiometric Dating Naturally-occurring radioactive materials break down into other materials at known rates. This is known as radioactive decay. Radioactive parent elements decay to stable daughter elements.