On his return to England, in October 1836, Darwin at once took his place among the acknowledged men of science of his country. For a time his health continued to be such as to allow him to get through a large amount of work. The next two years, which in his own opinion were the most active of his life, were spent, partly at Cambridge and partly in London, in the preparation of his _Journal of Researches_, of the zoological and geological results of the voyage, and of various papers for the Geological and Zoological Societies. So keen was his geological zeal that, almost against his better judgment, he was prevailed upon to undertake the duties of honorary secretary of the Geological Society, an office which he continued to hold for three years. And at each period of enforced holiday, for his health had already begun to give way, he occupied himself with geological work in the field. In the Midlands he watched the operations of earth-worms, and began those inquiries which formed the subject of his last research, and of the volume on _Vegetable Mould_ which he published not long before his death. In the Highlands he studied the famous Parallel Roads of Glen Roy; and his work there, though in after years he acknowledged it to be 'a great failure,' he felt at the time to have been 'one of the most difficult and instructive tasks' he had ever undertaken. In the beginning of 1839 Darwin married his cousin, daughter of Josiah Wedgwood, and grand-daughter of the founder of the Etruria Works, and took a house in London. But the entries of ill-health in his diary grow more frequent. For a time he and his wife went into society, and took their share of the scientific life and work of the metropolis. But he was compelled gradually to withdraw from this kind of existence which suited neither of them, and eventually they determined to live in the country. Accordingly, he purchased a house and grounds at Down in a sequestered part of Kent, some twenty miles from London, and moved thither in the autumn of 1842. In that quiet home he passed the remaining forty years of his life. It was there that his children were born and grew up around him, that he carried on the researches and worked out the generalisations that have changed the whole realm of science, that he received his friends and the strangers who came from every country to see him; and it was there that, after a long and laborious life, full of ardour and work to the last, he died at the age of seventy-three, on the 19th of April, 1882.