Royal Irish Academy

A Revolution in Profiles - Co. Offaly

In association with The Royal Irish Academy

John Joly 1857-1933

John Joly was born at Hollywood House, Bracknagh in 1857. His father John Plunket Joly served as Church of Ireland rector to Clonbullogue and the Joly family owned 500 acres in the locality. John’s mother, Julia Anna Maria Georgina Joly had been born comtesse de Lusi and traced her ancestry to the deposed Bourbon royalty of France.

Raised in Bracknagh, Joly lectured at Trinity College Dublin and emerged as one of the great Irish polymaths of the late 19th and early 20th centuries. He invented the meldometer to measure the melting point of minerals, the calorimeter to determine the heat of chemical reactions and a photometer to compare light sources. His ‘Joly Process’ was later utilised by Kodak to allow for colour photography, he pioneered the use of radium in cancer treatment.

The recipient of several national and international awards, during his lifetime he produced over 200 scientific papers and several books on a vast variety of subjects. Despite his lifelong affinity to Trinity, he travelled extensively and was a keen yachts man. He served as a commissioner of Irish Lights and president of the Royal Dublin Society.

When the rising broke out on Easter Monday, Trinity was virtually abandoned. The college’s chief steward Joseph Marshall ordered the gates locked and recruited a small band of 44 defenders consisting of colonial troops on furlough in Dublin, students and members of staff including 58-yearold Professor John Joly, who was in no doubt of the danger which the rebellion posed…

‘Was this indeed to be, perhaps, the last night of our ancient University? The question is no mere extravagance of the imagination. For so much of the very existence of so venerable a foundation is bound up with its century-old buildings, with its literary and artistic treasures, that sack and conflagration in a single night might obliterate practically all but its memory from the earth. So might perish Ireland’s most priceless treasure – the University of Berkeley, Goldsmith, Burke, Hamilton, and Lecky.’ (1)

Joly performed sentry duty and scouted around the city to obtain information. On Tuesday, he was present when Volunteer Gerald Keogh, who had been shot by one of the Trinity garrison was brought into the college grounds…

‘Later I saw him. In no irreverent spirit I lifted the face cloth. He looked quite young; one might almost call him a boy. The handsome waxen face was on one side concealed in blood. Poor boy! What crime was his? That of listening to the insane wickedness and folly preached by those older and who ought to be wiser than he.’ (1)

On Tuesday morning the college was occupied by a large force of British Military and its informal defence body stood down.

In Joly’s memoir ‘Reminiscences and anticipation‘ published in in 1920, his experiences of the Rising are dealt with in a chapter entitled ‘In the Trinity College during the Sinn Fein Rebellion by One of the Garrison

John Joly passed away at his home ‘Somerset’ on Temple Road, Dublin in December 1933. On his death the Irish Times commented…

‘Ireland has lost a most distinguished man of science, a scholar and student, whose work in the field of science had won for him international repute.’ (2)

The annual Joly lecture is held at Trinity in his honour.

Joly was buried at Mount Jerome cemetery following a funeral service at Trinity college chapel.


1901 and 1911 Census. Search online at

Daithí O Corráin and Eunan O’Halpin. The dead of the Irish Revolution. (Yale) 2020. Ciaran Reilly. Edenderry 1916 and the revolutionary era. (Edenderry) 2016.

Patrick N. Wyse Jackson: John Joly Dictionary of Irish Biography online at

John Joly. ‘In Trinity College during the Sinn Fein rebellion’ in ‘Reminiscences and anticipations’ republished in Rising’ In Offaly Heritage 9 edited by Ciaran Reilly. (Tullamore) 2016.

Mary Mulvihill ‘The man who brought radiography forward’ online at

Irish Times. 9 December 1933. 16 December 1933.

Irish Press. 9 December 1933. 12 December 1933.

(1) John Joly. ‘In Trinity College during the Sinn Fein rebellion’ in ‘Reminiscences and anticipations’ republished in Rising’ In Offaly Heritage 9 edited by Ciaran Reilly. (Tullamore) 2016.

(2) Irish Times. 16 December 1933.

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