Macdonald, John (1769-1831), a military engineer, was the youngest son of Flora Macdonald, the Jacobite heroine. He was educated in Portree and Edinburgh, and in 1780 obtained an Indian cadetship. For about eight years he was military and civil engineer in Sumatra, becoming first lieutenant in 1794. He made many maps and charts of Sumatra, which are now in the British Museum, and made observations on the variation of the magnetic needle. In 1800 he retired on half-pay, and held various posts till he became field officer of the Cinque Ports Volunteers, when he made a reconnaissance in an open boat of the preparations for invasion at Boulogne. His engineering skill was best shown in his improvements of naval and military telegraphy. Macdonald became an F.R.S. in 1800. His writings include many translations and other works, among which are Experiments with Machine-driven Fuses for Time Signals (1819), A New System of Telegraphy (1817).