Lloyd, Rev. Humphrey

Rev. Humphrey Lloyd (1800-1881) was born and educated in Dublin. He graduated in 1819 from Trinity College and progressively rose through the ranks in the University of Dublin. He was Junior Fellow (1824), Professor of Natural and Experimental Science (1831), Senior Fellow (1843), Vice Provost (1862) and eventually Provost (1867-1881). He was President of the Royal Irish Academy from 1846-1851, and elected a member of the Royal Societies of London and Edinburgh. He was an active contributor to the annual proceedings of the British Association for the Advancement of Science. He was an outstanding teacher and educationalist, and was reputedly the driver in establishing the Trinity Engineering School in 1841 after the untimely death of his father in 1837.

Lloyd’s most celebrated experimental contribution was to demonstrate William Rowan Hamiltons’ theoretical prediction of ‘conical refraction’. Lloyd succeeded in giving a demonstration of the phenomena. He found in accordance with Hamilton’s predictions the direction of polarization of the rays making up the luminous cone for both ‘internal and external’ conical refraction [1]. The experiment was celebrated in its day as being the historic equivalent of the discovery of Neptune from its theoretical prediction by Le Verrier and Johann Gottfried Galle in Berlin in 1846. Lloyd’s other contributions to optics include a report to the British Association on the state of the subject in 1833, two textbooks expounding the wave theory (while this was still contentious), and an important study of reflection and refraction by thin plates. In 1834 Lloyd made a contribution to optics examining Fresnels’ classic experiment of a fundamental new discovery of a half-wavelength phase acceleration that takes place upon reflection by a higher density medium. His experiment is remembered today in most physics experimental programmes as the Lloyd’s Mirror experiment.

The bulk of his remaining research work was devoted to terrestrial magnetism. At a time of rapidly developing international competition, magnetism became a hot topic after Sir John Ross discovered in 1832 a magnetic pole in Arctic Canada. In 1831-1832 he had already proposed that the British Association conduct a series of observations of the earth’s magnetic field, to be made in various parts of the kingdom. Lloyd was appointed to a committee to coordinate this activity, which he undertook effectively, and he scientifically led the project. A series of magnetic observations in Ireland were at the outset undertaken in twenty-four locations in collaboration with Sir Edward Sabine. Lloyd importantly invented a new technique for the simultaneous determination of magnetic inclination and intensity. It was the discovery of temporal variations in the earth’s magnetic field in 1838 that provided the momentum for the establishment of permanent observatories capable of making simultaneous measurements in different parts of the world. The British Association with government financial support, undertook the construction of these stations and assigned Lloyd the important job of drawing up instruction for the observers. Lloyd’s own observatory in Trinity College had been constructed under his supervision in 1837, and became the prototype to be established around the British Dominions. Lloyd received and coordinated their observations. Lloyd designed a range of equipment for measurements in these observatories and naturally undertook the training of the officers in charge in his Trinity observatory. The Grubb family manufactured most of these instruments in Rathmines. As Lloyd’s administrative load increased later in his career he remarkably remained active in his research with a late success of demonstrating the existence of currents of electricity in the earth’s crust.  He computed their effect on the daily variation in the magnetic field. He died in 1881 and is buried in Mount Jerome Cemetery.

2 Humphrey Lloyd, (2009) Account of the Magnetic Observatory of Dublin and the Instruments and Methods of Observation Employed there, Kessinger Publishers.

3 Lloyd, Humphrey, (2008), Complete Dictionary of Scientific Biography.

4 John Cawood, (1977), Terrestrial magnetism and the development of international collaboration in the early nineteenth century Annals of Science, Vol. 34, issue 6 Nov. pp. 551-587.