Complex sentence: By the next morning of January 1,1700, the sister was completely well, Mother Marguerite had a raging fever, suffered 12 days, and died on January 12,1700.
Split into simpler sentences: By the next morning of January 1,1700, the sister was completely well. But, Mother Marguerite had a raging fever, suffered 12 days, and died on January 12,1700.