Darwin and Lyell now became very intimate friends. "I am coming into your way, of only working about two hours at a spell," he writes to Lyell; "I then go out and do my business in the streets, return and set to work again, and thus make two separate days out of one." Of Lyell he said: "One of his chief characteristics was his sympathy with the work of others.... The science of geology is enormously indebted to Lyell--more so, as I believe, than to any other man who ever lived." The "Journal" was published in 1839. January twenty-nine of this year, Mr. Darwin, now thirty years of age, was married to his cousin, Emma Wedgwood, daughter of Josiah Wedgwood of Maer, and granddaughter of the founder of the potteries of Etruria. The extreme happiness of his married life proved the wisdom of his choice. He said in after years, "No one can be too kind to my dear wife, who is worth her weight in gold many times over." 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.