| A. Ba. | Adolfo Bartoli (1833–1894).- Formerly Professor of Literature at the Istituto di Studi superior at Florence. Author of Studia della letteratura Italiana; &c.
|  | Italian Literature (in part). |
| A. Bo.* | Auguste Boudinhon, D.D., D.C.L.- Professor of Canon Law at the Catholic University of Paris. Honorary Canon of Paris. Editor of the Canoniste contemporain.
| | Index Librorum Prohibitorum; Infallibility. |
| A. Cy. | Arthur Ernest Cowley, M.A., Litt.D.- Sub-Librarian of the Bodleian Library, Oxford. Fellow of Magdalen College.
|  | Ibn Gabirol;
Inscriptions: Semitic. |
| A. C. G. | Albert Charles Lewis Gotthilf Gunther, M.A., M.D., Ph.D., F.R.S.- Keeper of Zoological Department, British Museum, 1875–1895. Gold Medallist, Royal Society, 1878. Author of Catalogues of Colubrine Snakes, Batrachia Salientia, and Fishes in the British Museum; Reptiles of British India; Fishes of Zanzibar; Reports on the “Challenger” Fishes; &c.
|  | Ichthyology (in part). |
| A. E. G.* | Rev. Alfred Ernest Garvie, M.A., D.D.- Principal of New College, Hampstead. Member of the Board of Theology and the Board of Philosophy, London University. Author of Studies in the inner Life of Jesus; &c.
|  | Immortality;
Inspiration. |
| A. E. H. L | Augustus Edward Hough Love, M.A., D.Sc., F.R.S.- Sedleian Professor of Natural Philosophy in the University of Oxford. Hon. Fellow of Queen's College, Oxford; formerly Fellow of St John's College, Cambridge. Secretary to the London Mathematical Society.
| | Infinitesimal Calculus. |
| A. F. C. | Alexander Francis Chamberlain, A.M., Ph.D.- Assistant Professor of Anthropology, Clark University, Worcester, Massachusetts. Member of American Antiquarian Society; Hon. Member of American Folk-lore Society. Author of The Child and Childhood in Folk Thought.
| | Indians, North American. |
| A. G. | Major Arthur George Frederick Griffiths (d. 1908).- H.M. Inspector of Prisons, 1878–1896. Author of The Chronicles of Newgate; Secrets of the Prison House; &c.
| | Identification. |
| A. Ge. | Sir Archibald Geikie, LL.D.- See the biographical article, Geikie, Sir A.
| | Hutton, James. |
| A. Go.* | Rev. Alexander Gordon, M.A.- Lecturer on Church History in the University of Manchester.
| | Illuminati. |
| A. G. G. | Sir Alfred George Greenhill, M.A., F.R.S.- Formerly Professor of Mathematics in the Ordnance College, Woolwich. Author of Differential and Integral Calculus with Applications; Hydrostatics; Notes on Dynamics; &c.
| | Hydromechanics. |
| A. H.-S. | Sir A. Houtum-Schindler, C.I.E.- General in the Persian Army. Author of Eastern Persian Irak.
| | Isfahān (in part). |
| A. M. C. | Agnes Mary Clerke.- See the biographical article, Clerke, A. M.
| | Huygens, Christiaan. |
| A. N. | Alfred Newton, F.R.S.- See the biographical article, Newton, Alfred.
| | Ibis; Icterus. |
| A. So. | Albrecht Socin, Ph.D. (1844–1890).- Formerly Professor of Semitic Philology in the Universities of Leipzig and Tübingen. Author of Arabische Grammatik; &c.
| | Irak-Arabi (in part). |
| A. S. Wo. | Arthur Smith Woodward, LL.D., F.R.S.- Keeper of Geology, Natural History Museum, South Kensington. Secretary of the Geological Society, London.
| | Ichthyosaurus;
Iguanodon. |
| A. W. H.* | Arthur William Holland.- Formerly Scholar of St John's College, Oxford. Bacon Scholar of Gray's Inn, 1900.
| | Imperial Cities;
Instrument of Government. |
| A. W. Po. | Alfred William Pollard, M.A.- Assistant Keeper of Printed Books, British Museum. Fellow of King's College, London. Hon. Secretary Bibliographical Society. Editor of Books about Books and Bibliographica. Joint-editor of The Library. Chief Editor of the “Globe” Chaucer.
| | Incunabula. |
| A. W. R. | Alexander Wood Renton, M.A., LL.B.- Puisne judge of the Supreme Court of Ceylon. Editor of Encyclopaedia of the Laws of England.
| | Inebriety, Law of;
Insanity: Law. |