Complex sentence: In 1859 on a third foreign tour of eighteen months, in Europe with his wife and daughters, Dr. Frothingham became first aware of a defect in his own vision.
Split into simpler sentences: In 1859 on a third tour of eighteen months, in Europe was made with his wife and daughters. It was in the course of this journey that Dr. Frothingham became first aware of a defect in his own vision.