Gideon Algernon, a distinguished geologist and palaeontologist, was born at Lewes in Sussex in 1790. Having chosen the profession of a physician he commenced his career in his native town, where he soon established for himself an extensive practice, and began to cultivate the literature of his profession by contributions to medical journals. But it was as a man of science and as a lecturer that Mantell was destined to become known, and the accident of his position at Lewes, in the neighbourhood of an unwrought mine, by attracting his quick observation, and kindling his natural enthusiasm, directed his active energies towards that study which he afterwards enriched so greatly by discovery, and rendered so highly attractive by his happy talent for popular exposition. A richer field for observation and for the exercise of scientific tastes could scarcely have been found than that into which Dr Mantell was thrown, and few could have seized the opportunity with more zeal, or improved it with greater success. Previous to the time that he commenced his labours little was known of the nature of the Wealden formation, or of the fossils which it contained. Dr Mantell in a few years collected together from the Wealden and the chalk a museum of specimens of extinct reptiles, fishes, insects, and plants, which the trustees of the British Museum have since, at an expense of L5000, made the property of the nation, and which alone would have been sufficient to have gained for the collector a permanent position among the promoters of geological science. The discovery and demonstration of four out of five of the strange genera of extinct Dinosaurian reptiles—viz., the Iguanodon, Hypsilophodon, Pelorosaurus, and Regnosaurus—are owing to Dr Mantell; and some of the most perfect existing remains of those singular creatures are to be found in the valuable collection of the Wealden geologist. Dr Mantell was elected a member of the Royal Society in 1825; and in recognition of his valuable labours in the comparative anatomy of fossils, and in his discovery of fossil reptiles, he was adjudged the Wollaston medal and prize by the Geological Society in 1835. During the same year he removed from Lewes to Brighton; and four years afterwards he came to London, and resided first at Clapham, and afterwards at Chester Square, still continuing his medical practice, and prosecuting with unflagging activity his favourite geological researches. In 1849 the council of the Royal Society presented Dr Mantell with the Royal Medal in acknowledgment of his discoveries in palaeontology. He died at Chester Square, London, on the 10th of November 1852, aged sixty-two.

Dr Mantell did not take the position of a great generalizer or of the discoverer of new laws, yet his uncommon scientific ardour, combined with the accident of his position, and the requirements of the science, made him a great geologist. His success as a public teacher, as a popular expounder of geological facts, was unsurpassed during his time. By his numerous writings he has made a valuable addition to the geological literature of the British Islands. From 1813, when he published his first paper on the organic remains discovered in the environs of Lewes, to within a short period of his death, his literary labours were unceasing. In the Bibliographia Zoologiae et Geologiae of the Royal Society, the names of sixty-seven papers and works are given from Dr Mantell's pen. The most important of his works are—"On the Iguanodon, a newly discovered fossil reptile, from the strata of Tilgate Forest, in Sussex," &c., Phil. Trans., cxv.; "On the Discovery of the Hypsilophodon," &c., Proc. Geol. Soc. 1822; Illustrations of the Geology of Sussex, &c., London, 4to, 1827; The Geology of the South-East of England, 8vo, London, 1838; The Wonders of Geology, 2 vols. 8vo, London, 1838; The Medals of Creation, or First Lessons in Geology, 2 vols. 8vo, London, 1844. The last two works, besides meeting with a great degree of popularity in this country, have both been translated into German.