With his partner, John Gaff Gillespie, he developed an attenuated high-rise style for the office buildings of the fin de siecle cities.
James junior attended classes at Glasgow School of Art from 1888 until 1895, and completed his apprenticeship in the office of William Leiper (1839–1916).
On completion of his articles he undertook a grand tour, taking in France, Germany, Switzerland, Norway, Belgium, Holland, Austria, Hungary, Romania, Turkey, Greece and Spain.
He continued to undertake study tours to Europe, and was admitted as a Fellow of the Royal Institute of British Architects (RIBA) in 1906.
In 1904-5 Salmon was responsible for the Lion Chambers on Hope Street, an early example of reinforced concrete construction.