Complex sentence: Miss Swallow taught, tutored, and cleaned for years, finally saving enough to enter Vassar College in 1868, earning her bachelor's degree in two years; she earned a master of arts degree for her thesis on the chemical analysis of iron ore.
Split into simpler sentences: Miss Swallow taught, tutored, and cleaned for years, finally saving enough to enter Vassar College in 1868, earning her bachelor's degree in two years. And later, a master of arts degree for her thesis on the chemical analysis of iron ore.