School Society

The Joly Society

John Joly Was an Irish Geologist, Physicist and Engineer who held the Chair of Geology and Mineralogy from 1897 until his death in 1933.

He entered Trinity College in 1876, graduating in Engineering in 1882 in first place with various special certificates in branches of engineering, at the same time obtaining a First Class Honours in modern literature. He worked as a demonstrator in Trinity's Engineering and Physics departments before succeeding William Johnston Sollas in the Chair of Geology and Mineralogy in 1897.

Joly joined the Royal Dublin Society in 1881 while still a student, and was a frequent contributor of papers. His first scientific paper was published in 1883, on the use of meteorological instruments at a distance. During his career he wrote over 270 books and scientific papers.

On 17 May 1899 Joly read his paper, "An Estimate of the Geological Age of the Earth" to the Royal Dublin Society. In it, he proposed to calculate the age of the earth from the accumulation of sodium in the waters of the oceans. He calculated the rate at which the oceans should have accumulated sodium from erosion processes, and determined that the oceans were about 80 to 100 million years old. Although this method was later considered inaccurate and was consequently superseded, it radically modified the results of other methods in use at the time.

Along with his friend Henry Horatio Dixon, Joly also put forward the cohesion-tension theory which is now thought to be the main mechanism for the upward movement of water in plants.

After his death, his friends subscribed the sum of £1,700 to set up a memorial fund which is still used to promote the annual Joly Memorial Lectures at the University of Dublin, which were inaugurated by Sir Ernest Rutherford in 1935

“The sediments of the past are many miles in collective thickness: yet the feeble silt of the rivers built them all from base to summit. “ - John Joly