Dr Jonsz, a miscellaneous writer, descended from an old Scottish family, was born at Guernsey in 1773. While still a child, he removed with his family to Cornwall, and after attending several schools, was at last sent in 1787 to the grammar school of Lostwithiel. In 1790 he began the study of medicine at Edinburgh; and at the early age of eighteen received the diploma of physician. Too young, however, for private practice, he remained in Edinburgh for five years, and after filling successively the offices of assistant-surgeon in the artillery, and chemist to the Board of Ordnance, he settled in 1807 as a physician at Blackheath. This profession he relinquished in 1811, and for several years afterwards he was employed by government in making various surveys in Scotland. Of these, the most important was his mineralogical and geological survey of that country, begun in 1826 and completed in 1832. He died at Penzance in 1835, from the effects of a fall. At the period of his death Dr Macculloch was lecturer on geology and chemistry in the military establishment at Addiscombe. He had also been appointed, in 1820, physician in ordinary to Leopold of Saxe-Coburg, and was fellow of the Royal, Linnean, and Geological Societies. In addition to the knowledge of mathematics, geology, mineralogy, medicine, chemistry, and theology, displayed in his various works, he possessed an acquaintance with physics, botany, zoology, astronomy, and the mechanical arts. He was also skilled in music, drawing, and architecture. He published Remarks on the Art of Making Wine, 12mo, 1816; A Description of the Western Islands of Scotland, in 2 vols. 8vo, London, 1819; A Geological Classification of Rocks, 8vo, London, 1821; and The Highlands and Western Islands of Scotland, containing Descriptions of the Scenery, Antiquities, &c., in 4 vols. 8vo, London, 1824. In 1837 was published his posthumous work, entitled Proofs and Illustrations of the Attributes of God from the Facts and Laws of the Physical Universe, being the Foundation of Natural and Revealed Religion, in 3 vols. 8vo, London. He also contributed several papers to the seventh edition of this Encyclopaedia, to the Transactions of the Geological Society, to the Edinburgh Review, and to other periodicals.