248 LIFE OF DARWIN 



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 com- 

 pelled gradually to withdraw from this kind of existence 

 which suited neither of them, and eventually they de- 

 termined to live in the country. Accordingly, he 

 purchased a house and grounds at Down in a seques- 

 tered 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 



