Note: Cowles is credited in WorldCat library records, and British Library records, chiefly for more than a dozen volumes in the Macdonald Illustrated Edition (UK publisher Macdonald) of H. Rider Haggard novels. He contributed illustrations to UK weeklies during the 1920s and 1930s, including The Sphere, at least 1925 to 1940; and The Tatler and/or The Bystander, at least 1921 to 1930 (from online search for credits under his full name).