They lived at No. 12 Upper Gower Street, as he wrote a college mate, "a life of extreme quietness.... We have given up all parties, for they agree with neither of us; and if one is quiet in London, there is nothing like its quietness."

In 1842, his "Structure and Distribution of Coral Reefs" was published, a book which cost him, he says, "twenty months of hard work, as I had to read every work on the islands of the Pacific, and to consult many charts." Of this book, Professor Geikie says: "This well known treatise, the most original of all its author's geological memoirs, has become one of the classics of geological literature. The origin of those remarkable rings of coral-rock in mid-ocean has given rise to much speculation, but no satisfactory solution of the problem has been proposed. After visiting many of them, and examining also coral reefs that fringe islands and continents, he offered a theory which, for simplicity and grandeur, strikes every reader with astonishment.... No more admirable example of scientific method was ever given to the world, and, even if he had written nothing else, this treatise alone would have placed Darwin in the very front of investigators of nature."

Lyell wrote to Darwin concerning this book: "It is all true, but do not flatter yourself that you will be believed till you are growing bald, like me, with hard work and vexation at the incredulity of the world."

Darwin's next work, on the "Volcanic Islands Visited during the Voyage of the Beagle," was published in 1844. This book, he said, "cost me eighteen months." His third geological book, "Geological Observations on South America," was published in 1846.

Meantime, tired of smoky London, Darwin purchased a home in Down, a retired village five or six hundred feet above the sea. The house was a square brick building, of three stories, vine-covered, in the midst of eighteen acres. "Its chief merit," Darwin writes to a friend, "is its extreme rurality. I think I was never in a more perfectly quiet country." Here, for forty years, Darwin lived the isolated life of a student, producing the books that made him the most noted scientist of his century. Of these years, Mr. Darwin said: "Few persons can have lived a more retired life than we have done. Besides short visits to the houses of relations, and occasionally to the seaside or elsewhere, we have gone nowhere. During the first part of our residence we went a little into society, and received a few friends here; but my health almost always suffered from the excitement.... I have, therefore, been compelled for many years to give up all dinner parties.... From the same cause I have been able to invite here very few scientific acquaintances. My chief enjoyment and sole employment throughout life has been scientific work; and the excitement from such work makes me for the time forget, or drives quite away, my daily discomfort."

At Down, Darwin worked for eight years on two large volumes concerning cirripedia (barnacles), describing all the known living species; the extinct species, or fossil cirripedes, were in two smaller volumes. The first books were published by the Ray Society, between 1851 and 1854; the others by the Palæontographical Society. About two years out of the eight were lost through illness. Sometimes he became half discouraged. He wrote a friend, "I have been so steadily going downhill, I cannot help doubting whether I can ever crawl a little uphill again. Unless I can, enough to work a little, I hope my life may be very short, for to lie on a sofa all day and do nothing but give trouble to the best and kindest of wives and good, dear children is dreadful."

Darwin doubted, in after life, "whether the work was worth the consumption of so much time," but Professor Huxley thinks he "never did a wiser thing than when he devoted himself to the years of patient toil which the cirriped-book cost him.... The value of the cirriped monograph lies not merely in the fact that it is a very admirable piece of work, and constituted a great addition to positive knowledge, but still more in the circumstance that it was a piece of critical self-discipline, the effect of which manifested itself in everything he wrote afterwards, and saved him from endless errors of detail." Darwin's patient labor is shown by his working "for the last half-month, daily, in dissecting a little animal about the size of a pin's head, from the Chonos archipelago, and I could spend another month, and daily see more beautiful structure."

During these years from 1846 to 1854, death had twice disturbed the quiet life at Down. In 1849, Dr. Darwin died, and his son Charles was so ill that he could not attend the funeral. In 1851, Annie Darwin died, at the age of ten, after a brief illness. "She was," said Darwin, "my favorite child; her cordiality, openness, buoyant joyousness, and strong affections made her most lovable.... When quite a baby, this [strong affection] showed itself in never being easy without touching her mother when in bed with her; and quite lately she would, when poorly, fondle for any length of time one of her mother's arms.... She would at almost any time spend half an hour in arranging my hair, 'making it,' as she called it, 'beautiful,' or in smoothing, the poor, dear darling, my collar or cuffs—in short, in fondling me.... Her whole mind was pure and transparent. One felt one knew her thoroughly and could trust her. I always thought that, come what might, we should have had, in our old age, at least one loving soul which nothing could have changed.

"All her movements were vigorous, active, and usually graceful. When going round the Sandwalk with me, although I walked fast, yet she often used to go before, pirouetting in the most elegant way, her dear face bright all the time with the sweetest smiles. Occasionally she had a pretty coquettish manner towards me, the memory of which is charming....

"In the last short illness her conduct, in simple truth, was angelic. She never once complained; never became fretful; was ever considerate of others, and was thankful in the most gentle, pathetic manner for everything done for her. When so exhausted that she could hardly speak, she praised everything that was given her, and said some tea 'was beautifully good.' When I gave her some water, she said, 'I quite thank you;' and these, I believe, were the last precious words ever addressed by her dear lips to me."