Complex sentence: Mary Maverick bore ten children over a span of 21 years; four died of illness before the age of eight, which led Mary to seek solace in the spiritualism which was increasing in popularity in mid-nineteenth-century America.
Split into simpler sentences: Mary Maverick bore ten children over a span of 21 years. Four died of illness before the age of eight, which led Mary to seek solace in the spiritualism which was increasing in popularity in mid-nineteenth-century America.