Complex sentence: The French progressively assumed more of the important administrative positions, and by 1884 they directed, or supervised the Tunisian administration of, government bureaus dealing with finance, post, education, telegraph, public works and agriculture.
Split into simpler sentences: The French progressively assumed more of the important administrative positions. By 1884 they directed or supervised the Tunisian administration of government bureaus dealing with finance, post, education, telegraph, public works and agriculture.