Complex sentence: About 1867 Honoré Fisquet undertook the publication of an episcopal history of France (La France Pontificate) in which for the early period he should utilize the "Gallia", at the same time bringing the history of each diocese down to modern times.
Split into simpler sentences: About 1867 Honoré Fisquet undertook the publication of an episcopal history of France, "La France Pontificale". For the early period he should used the "Gallia", at the same time bringing the history of each diocese down to modern times.