Changes

* The measurements of underground temperatures near Edinburgh served as basis for the estimated “general increase of temperature in the Earth downwards” alias mean geothermal gradient of 1/50th of a degree Fahrenheit per foot (~ ca 36°C/km).

* The measurements of underground temperatures near Edinburgh served as basis for the estimated “general increase of temperature in the Earth downwards” alias mean geothermal gradient of 1/50th of a degree Fahrenheit per foot (~ ca 36°C/km).

After taking into account the estimated uncertainties in thermal gradient and thermal conductivity, Kelvin broadened an upper limit for the age of the Earth to interval between 20 and 400 millions of years (20 ~ 400 Ma). In a later paper, based on experimental results performed by Carl Barus (who found out that diabase, a typical basalt of very primitive character, melts between 1100°C and 1170°C and is thoroughly liquid at 1300°C)<ref name="KelvinNature1895">{{cite journal |title=On the Age of the Earth |author= Lord Kelvin |journal= Nature (reprint in SA)|date= January 3, 1895 |pages= 334-337 |url=http://www.scientificamerican.com/article/lord-kelvin-on-the-age-of-the-earth/ |accessdate=14 June 2015 |quote= Carl Barus (Phil. Mag., 1893, first half year, pp. 186, 187, 301-305) that diabase, a typical basalt of very primitive character, melts between 1,100° C. and 1,170° and is thoroughly liquid at 1,300°.}}</ref>, he modified the value for supposed initial molten rock temperature to 1200°C<ref name="Richter"/>, thus by the end of the 1800s narrowed down the interval to 20 ~ 40Ma<ref name="chemeu">{{cite web |title=William Thomson, 1st Baron Kelvin |publisher=chemeurope.com |url=http://www.chemeurope.com/en/encyclopedia/William_Thomson%2C_1st_Baron_Kelvin.html |accessdate=14 June 2015 |quote= Thomson ultimately settled on an estimate that the Earth was 20-40 million years old }}</ref>, with personal preference for the lower value which is also the most quoted one.<ref>{{cite book |title= The Dating Game: One Man's Search for the Age of the Earth  |author= Cherry Lewis  |publisher= Cambridge University Press |year= 2012 |pages= 39 |isbn= 978-11076-59599 |url= https://books.google.com/books?id=vU1yZQ03Kz0C }}</ref><ref name="West"/>

After taking into account the estimated uncertainties in thermal gradient and thermal conductivity, Kelvin broadened an upper limit for the age of the Earth to interval between 20 and 400 millions of years (20 ~ 400 Ma). In a later paper, based on experimental results performed by Carl Barus (who found out that diabase, a typical [[basalt]] of very primitive character, melts between 1100°C and 1170°C and is thoroughly liquid at 1300°C)<ref name="KelvinNature1895">{{cite journal |title=On the Age of the Earth |author= Lord Kelvin |journal= Nature (reprint in SA)|date= January 3, 1895 |pages= 334-337 |url=http://www.scientificamerican.com/article/lord-kelvin-on-the-age-of-the-earth/ |accessdate=14 June 2015 |quote= Carl Barus (Phil. Mag., 1893, first half year, pp. 186, 187, 301-305) that diabase, a typical basalt of very primitive character, melts between 1,100° C. and 1,170° and is thoroughly liquid at 1,300°.}}</ref>, he modified the value for supposed initial molten rock temperature to 1200°C<ref name="Richter"/>, thus by the end of the 1800s narrowed down the interval to 20 ~ 40Ma<ref name="chemeu">{{cite web |title=William Thomson, 1st Baron Kelvin |publisher=chemeurope.com |url=http://www.chemeurope.com/en/encyclopedia/William_Thomson%2C_1st_Baron_Kelvin.html |accessdate=14 June 2015 |quote= Thomson ultimately settled on an estimate that the Earth was 20-40 million years old }}</ref>, with personal preference for the lower value which is also the most quoted one.<ref>{{cite book |title= The Dating Game: One Man's Search for the Age of the Earth  |author= Cherry Lewis  |publisher= Cambridge University Press |year= 2012 |pages= 39 |isbn= 978-11076-59599 |url= https://books.google.com/books?id=vU1yZQ03Kz0C }}</ref><ref name="West"/>

Many scientists liked these values, since they appeared to be consistent with calculations made by [[Hermann von Helmholtz]], who in 1854 estimated the age of sun to be between 20 and 40 million years,<ref name="ingv"/><ref>{{cite web |title= Trial balloons and the age of the earth |author= Tas Walker |publisher=CMI |url= http://creation.com/trial-balloons-geochronology |accessdate= 14 June 2015}}</ref> but for both evolutionists in biology as well as uniformitarians in geology they were distastefully low.<ref name="KelvinRevisited">{{cite web |title= Lord Kelvin revisited on the young age of the earth |author= John Woodmorappe |publisher=CMI |url= http://creation.com/trial-balloons-geochronology |accessdate= 14 June 2015}}</ref> Darwin wrote in his letters that he has ''“not as yet been able to digest the fundamental notion of the shortened age of the sun and earth,”''<ref>{{cite book |author= Loren Eiseley

Many scientists liked these values, since they appeared to be consistent with calculations made by [[Hermann von Helmholtz]], who in 1854 estimated the age of sun to be between 20 and 40 million years,<ref name="ingv"/><ref>{{cite web |title= Trial balloons and the age of the earth |author= Tas Walker |publisher=CMI |url= http://creation.com/trial-balloons-geochronology |accessdate= 14 June 2015}}</ref> but for both evolutionists in biology as well as uniformitarians in geology they were distastefully low.<ref name="KelvinRevisited">{{cite web |title= Lord Kelvin revisited on the young age of the earth |author= John Woodmorappe |publisher=CMI |url= http://creation.com/trial-balloons-geochronology |accessdate= 14 June 2015}}</ref> Darwin wrote in his letters that he has ''“not as yet been able to digest the fundamental notion of the shortened age of the sun and earth,”''<ref>{{cite book |author= Loren Eiseley