This paper is an abbreviated version of one of the three annual Edinburgh University “Town and Gown” lectures. It was given in the City Chambers, Edinburgh, on 3rd March 1964. The deleted material was largely references to Negroes in Scotland. The oratorical overtones, however, have been faithfully preserved. Because of its extensive range, documentation has not been added, but any readers who would like specific references should write to Professor Shepperson at the History Department, Edinburgh University, Scotland.