Joly, John (1857-1933) was an Irish scientist. He is known for a remarkable variety of inventions and contributions to botany, geology, medicine, photography, and physics.
In 1894, Joly and the Irish botanist Henry Dixon published a theory explaining how liquids moved within plants. Scientists today view the theory as correct. Also in 1894, Joly patented one of the first methods to produce color photographs . This technique, known as the “Dublin method” or the “Joly color process” involved placing a glass plate with hundreds of thin lines in red, blue, and yellow in front of a negative film. However, the process was not commercially successful.
Joly’s most influential work concerned the origin of continents and the age of Earth . He proposed that the heat of Earth’s interior was generated from the decay of radioactive elements. Joly proposed that convection currents of molten rock dragged Earth’s crust, which caused it to buckle and fold, creating mountains. These ideas, combined with work by other scientists, contributed to the modern theory of plate tectonics . Joly also attempted to determine the age of Earth by calculating the rate of accumulation of sediments and sodium in the oceans to reach their current levels. Joly calculated that oceans must have formed at least 80 million to 100 million years ago. Although this method was not accurate, Joly convinced many scientists that Earth was much older than many had previously thought.
Joly worked with the British physicist Ernest Rutherford, on a radiometric technique to determine the age of rocks. Radiometric methods are based on the fact that certain radioactive isotopes (forms of chemical elements) decay at a known rate. However, Joly’s technique was not as accurate as modern radiometric dating techniques. In 1914, he published on a method to effectively use radioactive radium to treat cancer . Joly’s technique was one of the first forms of radiotherapy in medicine. He also invented several measuring instruments used in physics research.
John Joly was born on Nov. 1, 1857, in Bracknagh, County Offaly, in Ireland. He studied engineering at Trinity College in Dublin , where he received a doctorate in 1882. He remained at Trinity for his entire career, where he held positions at various times in civil engineering, geology, mineralogy, and physics. He published more than 250 scientific papers and several books during his career. He was made a fellow (member) of the Royal Society in 1892. He died on Dec. 8, 1933.
