 In January 1916, Barr was given charge of a school for machinists in London, intended to supply workers to a nearby factory for machine guns for the war effort; the school closed that June, as the factory was unable to take on the new workers at the expected rate.In the early 1920s Barr was a frequent visitor to Alfred North Whitehead in Chelsea, London, but by 1924 he had moved back to New York.Hamlin Garland writes that, "after thirty years in London", Barr returned to America "in order that his young sons might become citizens".