Born in New York on Oct 30th, 1859, the younger son of Robert Caldwell, of Charleston, South Carolina. A relative, Charles Caldwell (d.1849), was a distinguished USA Army Surgeon and Professor of Natural History at the University of Pennsylvania. He studied Medicine at Westminster Hospital and acted as Assistant House Surgeon. He joined the RAMC as Surgeon on Jan 31st, 1885, and was promoted Surgeon Major on Jan 31st, 1899; Lieutenant-Colonel on Jan 31st, 1905, and Colonel on Jan 1st, 1917. He served with the Frontier Field Force in the Sudan campaign in 1885-1886, and received the Khedive’s Bronze Star. For his service in the South African War, 1899-1902, he was awarded the Queen’s and King’s Medals, as well as the Royal Humane Society’s Medal. He was next engaged in sanitary work, and was placed in charge of the Laboratories first at Meerut and afterwards at Aldershot, and was appointed the specialist sanitary officer to the Western Area at Devonport. He had retired when, during the War 1914-1919, he was put in charge of the Alexandra Hospital, Cosham, and the affiliated VAD establishments. He died in a Nursing Home at Babbacombe, Devon, on April 4th, 1919. Publications: “Prevention of Disease in Armies in the Field,” Parkes Memorial Prize Essay, London, 1904; New York, 1905. *Military Hygiene*, London and New York, 1905; 2nd ed., 1910. “Soil Pollution and Disease in Camps.” – *Brit. Med. Jour.*, 1903, i, 248. “Refuse Disposal in Camps.” – *Jour. State Med.*, 1903, ii, 384. “Causation of Enteric Fever apart from Water Supply.” – *Public Health*, London, 1903-4, xvi, 84. “Enteric Fever during Active Service.” – *Brit. Med. Jour.*, 1907, ii, 513. “Infant Mortality and Parliamentary Legislation.” – *Med. Press and Circ*., 1908, lxxxvi, 251. Other communications on sanitation.