In 1910, while still an undergraduate, a Devonian igneous rock from Norway was assigned an age of 370 Ma by the U-Pb method.
(‘The Association of Lead with Uranium in Rock-Minerals, and Its Application to the Measurement of Geological Time’, Proceedings of the Royal Society, Series A 85: 248–256, 1911).
Published at a time when the age of the Earth was in dispute, this result established Earth’s great antiquity compared to Biblical and other estimates.
In 1913, Holmes published the now-famous booklet ‘The Age of the Earth’, which established him as the world’s authority on geochronology.
When it comes to measuring the ages of things, we are told that there are a dozen different radioactive dating methods and that they all give the same answer. Fossil wood from a quarry near the town of Banbury, England, some 80 miles north-west of London, was dated using the carbon-14 method.Diamonds analyzed from mines in South Africa and Botswana, and from alluvial deposits in Guinea, West Africa, found measurable carbon-14—over ten times the detection limit of the laboratory equipment.