Superman, from Action Comics #27 (August, 1940)
Paul Henry Cassidy was the first ghost artist on the 'Superman' comic, from 1938 to 1940. The addition of a daily version increased the workload for Joe Shuster, so he assigned Cassidy to do the inking and the detail work. Prior to this, Cassidy had worked as a graphics arts teacher at the Milwaukee Vocational School. Cassidy added a bolder, darker and more fluid line to Shuster's style. After a while, Cassidy got to do entire stories by himself. Notable about Cassidy's 'Superman' was the addition of the 'S' symbol on the cape.
Cassidy was also possibly the first comic scholar ever, since he wrote a Master's Thesis about comics at the University of Wisconsin, as early as 1942. After leaving the Shuster studio in 1940, Leo Nowak succeeded him as the new 'Superman' assistant-illustrator. Cassidy landed a job at Field Enterprises in Chicago, where he worked as an artist for the World Book Encyclopedia and served as art director and managing director for its ChildCraft books. He later worked for Grolier's Book of Knowledge in New York City. In 1964, he returned to Milwaukee, where he headed the graphics arts department at the Milwaukee Area Technical College. Paul Cassidy passed away on 15 May 2005 in Milwaukee, Wisconsin at the age of 94.