1826 March 19
1873 April 24 Evidence of Marriage
Date Address Document
1826-57 Cork Directory
1873 Sandymount Green, Dublin  
1880 Idrone Terrace Directory
1884 Brookvale House, Bookvale Road, Donneybrook Directory
1894-1895 81 Marlboro Road, Donneybrook Directory
1901 Bray, Co Wicklow  
Date Employment Document
1849-1857 Librarian of Queen's College, Cork. Directories
1851 Member of the Royal Irish Academy  
1855 Professor of Physics at the Roman catholic University, Dublin  
1856-1872 Professor of Natural Philosophy, The Catholic University, Dublin Directories
1858-1869 F.R.S Directories
1870-1873 Vice-president of Royal Irish Academy Directories
1874-1884 Professor of Applied Mathematics, Royal College of Science, Dublin Directories
1880 & 1888 Dean of Royal College of Science, Dublin  
1890 Resigned F.R.S aged 65 (compulsory)  
1901 March 08 Evidence of Death

Rosetta is listed as widow in 1901 census, so it appears Henry died before this date.

HENNESSY, HENRY (1826-1901), physicist, born at Cork on 19 March 1826, was the second son of John Hennessy of Ballyhennessy, co. Kerry, by his wife Elizabeth, daughter of Henry Casey of Cork. Sir John Pope-Hennessy [q. v.] was a younger brother. Educated at Cork under Michael Healy, he received an excellent training in classics, modern languages, and mathematics. Deprived as a Roman catholic of a university education, he adopted the profession of an engineer. His leisure was from early youth devoted to mathematical research, in which he engaged quite spontaneously. From an early period he made original and valuable contributions to British and foreign scientific journals, which he continued through life. In 1849 he was made librarian of Queen's College, Cork, and in 1855, on the invitation of Cardinal Newman, he became professor of physics at the Roman catholic University, Dublin. In 1874 he transferred his services to the Royal College of Science, Dublin, where he was appointed professor of applied mathematics. His work there was of exceptional merit, and he was dean of the college in 1880 and again in 1888. Hennessy was made a member of the Royal Irish Academy in 1851, and was its vice-president from 1870 to 1873. He was also elected F.R.S. in 1858. In 1890 he resigned his chair under the recent compulsory rules for superannuation in the civil service at the age of 65. A memorial to the government protesting against his retirement was influentially signed but was without effect. Owing to the inadequacy of his pension he resided much abroad, but returning to Ireland under medical advice, he died on 8 March 1901, at Bray, co. Wicklow. He married Rosa, youngest daughter of Hayden Corri, and had issue

Hennessy was remarkable for his versatile interests and scientific ingenuity. In his earliest paper, which was published in 1845, when he was only nineteen, in the 'Philosophical Magazine,' he proposed to use photography for the registration of barometric and thermometric readings. In 'Researches in Terrestrial Physics' (Phil. Trans. 1851) he argued from the figure and structure of the earth and planets, that they were of fluid origin, and that a fluid nucleus at a high temperature was enclosed within their crust. He also wrote on meteorology and on climatology (British Assoc. Rep. 1857), deducing laws which regulate the distribution of temperature in islands. The excellence of a paper 'On the Influence of the Gulf Stream' (Proc. Roy. Soc. 1857-9) led to a request to report on the temperature of the seas surrounding the British Isles for the Committee on Irish Fisheries in 1870. Among his other proposals was one for a decimal system of weights and measures founded on the length of the polar axis of the earth, a quantity capable of more accurate determination than the earth's quadrant, on which the metric system is based. Standards such as the polar foot and the polar pound, and a complete set of weights and measures on the polar system, constructed under Hennessy's supervision, are in the Museum of the Royal College of Science, Dubhn. In the same museum are many models of his mechanical inventions, one of them illustrating the structure of sewers best adapted to obtain the greatest scour with due provision for a great influx of storm water (cf. 'Hydraulic Problems on the Cross-sections of Pipes and Channels,' Proc. Roy. Soc. 1888). Hennessy, besides his papers in scientific periodicals, published separately : 1. 'On the Study of Science in its Relation to Individuals and Society,' Dublin, 1858; 2nd edit. 1859. 2. 'On the Freedom of Education' (a paper at the Social Science Congress, Liverpool, in 1858), 1859. 3. 'The Relation of Science to Modern Civilisation,' 1862.

Henry's correspondance with Charles Darwin

Books by Henry include The Figure and Primitive Formation of the Earth, or Researches in Terrestrial Physics.

On an Optical Phenomenon Observed in July, 1856, while on a Voyage to Havre
On Meteorology
On South European Plants Found Growing in the West and South of Ireland
On the Causes of Certain Phenomena Observed on Lough Erne
On the Distribution of Heat over the Island of Great Britain
On the Formation of Ground Ice in the Bed of the River Dodder
On the Föhn of the Alps, and Its Connexion with the Glacier Theories
On the Influence of the Earth's Internal Structure on the Length of the Day
On the Stability of the Earth's Axis of Rotation
On the Synchronous Distribution of Temperature over the Earth's Surface
Researches in Physical Geology. Part II.
Researches in Terrestrial Physics. Part II
Researches on Physical Geology.Part I. The Figure and Primitive Formation of the Earth.
The Figure and Primitive Formation of the Earth, or Researches in Terrestrial Physics. Part I
Evidence of Other Information