Complex sentence: His duties were light, allowing him many hours to read the books and examine the works in the store's print department; it was there that Sloan created his earliest surviving works, including pen and ink copies after Dürer and Rembrandt.
Split into simpler sentences: His duties were light, allowing him many hours to read the books and examine the works in the store's print department. It was there that Sloan created his earliest surviving works, among which are pen and ink copies after Dürer and Rembrandt.