We were recently inspired by a goireland.com feature on Irish inventors to take a look through our Irish family history records for some of these famous Irish men and woman who made a huge contribution to science, technology and engineering. In the second of our posts we take a look at the family history records of John Joly, famous geologist and physicist associated with discovering the first process for producing colour images.

John Joly was born 1st November 1857 in Bracknagh, Co. Offaly. He graduated from Trinity College Dublin with a Bachelor of Arts in Modern Literature and Bachelor of Engineering in 1883. He went on to become Assistant to the Professor of Civil Engineering at TCD, then Assistant to the Professor of Experimental Physics before being appointed Professor of Geology and Mineralogy in 1897.

He wrote over 270 books and scientific papers in his career. Some of which discovered or were the foundation for important discoveries in such varied fields as:

Scientific Instruments

He is credited with the invention of:

  • The meldometer:  for measuring the melting points of minerals
  • A steam calorimeter: for measuring specific heats
  • A photometer: for measuring light intensity


  • Joly is credited with having been the first to accurately estimate the age of a geological period – an essential step in estimating the age of the Earth.

Cancer Treatment

  • Working in collaboration with Dr Walter Stevenson’s he pioneered the use of radiation as a treatment for cancer.


  • Perhaps Joly’s most practical application of his great intelligence was his development and patenting of a method for producing colour photographs.



In the records on findmypast.ie we found a number related to Professor John Joly. In the first of two entries from Thom’s Directory of Ireland 1910 we can see Joly as a council member of the Biological Association of TCD:

In the second entries from  Thom’s Directory of Ireland 1910 we can see Joly residing in Somerset House, Temple Road, Rathmines:

The final entry see’s Joly listed in Thom’s Whos Who of Ireland 1923:

John Joly died in December 1933 and is remembered as one of Ireland’s, if not the World’s greatest scientists.