It was based on the idea that no significant source of novel heat energy was affecting the Earth.
This just goes to show that just because independent estimates of age seem to agree with each other doesn't mean that they're correct - despite the fact that this particular argument is the very same one used to support the validity of radiometric dating today.
Other factors and basic assumptions must also be considered.
As one answer to his critics, Kelvin produced a completely independent estimate -- this time for the age of the Sun.
His result was in close agreement with his estimate of the age of the earth.
NMGRL uses a 75 watt Photon Machines Fusions CO laser at NMGRL is used mainly for the total-fusion of sanidine crystals which include J-value determinations from Fish Canyon Tuff (FC-2) sanidine monitors.
Secondary ion mass spectrometry (SIMS) is a versatile technique for measuring the chemical and isotopic composition of solid materials on a scale of a few microns.
This estimate was actually reduced over his lifetime to between 20 Ma and 40 Ma and eventually to less than 10 Ma. Perry, in particular, a noted physicists and former assistant to Kelvin, showed that cooling calculations using different but equally likely assumptions and data resulted in ages for the Earth of as much as 29 Ga.
Of course, later scientists, like John Perry and T. After this came to light, Kelvin admitted that he might just as well have set his original upper limit on the age of the Earth at 4,000 Ma instead of 400 Ma.
These instruments will complement extant sector gas-source mass specs (MAP 215-50 and VG5400) that perform a variety of other noble gas measurements including 40Ar/39Ar dating.
We also have a state-of-the-art microscopy lab for sample preparation, and a Thermo Fisher Element2 high-resolution ICP-MS for measuring U-Th-Sm in He dating, as well as a wide range of other trace metals in many different types of samples. Below: Apatite (U-Th)/He cooling ages overlain on bedrock geology, faults and seismicity, slope, and precipitation maps, in the central Washington Cascades.
My research and that of my students, postdocs, and collaborators, covers a wide range, including experimental development of (U-Th)/He thermo- and geochronology, applications of thermochronology in tectonic geomorphology, and igneous geochemistry.