Complex sentence: While Bengough was probably the most significant pre- 20th Century Canadian cartoonist, Henri Julien was likely the most accomplished, and was published widely both at home and abroad, in periodicals such as "Harper's Weekly" and "Le Monde illustré".
Split into simpler sentences: While Bengough was probably the most significant pre- 20th Century Canadian cartoonist, Henri Julien was likely the most accomplished. Published widely both at home and abroad, Julien's cartoons appeared in periodicals such as "Harper's Weekly" and "Le Monde illustré".