Dickens has enjoyed a popularity probably unparalleled among English writers. Forster has calculated that during the twelve years succeeding his death no fewer than 4,239,000 volumes of his works were sold in Britain. The secret was in the first place originality. Dickens had lived the life he depicted. With a strong memory and keen powers of observation he had been storing up from early boyhood information which in his maturer years served him well. 'Sam's knowledge of London was extensive and peculiar,' he writes of Weller, when Mr. Pickwick addresses him with a sudden query about the nearest public house; and he illustrates Sam's knowledge by making him answer without a moment's hesitation. Dickens himself, if put down suddenly in any quarter of London, could probably have answered the question with equal readiness. He was emphatically a man of cities, was restless when he was long away from streets, and loved above all things the streets of London. But he was still more an observer of persons than an observer of places. Even in boyhood he judged men with great accuracy; and after he had won fame he asserted that he had never seen cause to change the secret impression of his boyhood with regard to anyone whom he had known then. Moreover, he never forgot. In his troubled and wretched boyhood, therefore, he was 'making himself,' though involuntarily and in an unpleasant fashion, as much as Scott was by his Liddesdale raids. It is however the something added to observation that gives literary value; and had Dickens added nothing he would have been far on the way to oblivion now. Shakespeare may have based Falstaff on observation; but probably no man, except Shakespeare himself, was ever quite as humorous as the fat knight. Similarly, it is safe to assert that Dickens never met a Londoner with all the wit and resource of Sam Weller. 'The little more, and how much it is.' What the artist adds creates the character. Incidents he has seen, phrases he has heard, are only the raw material for his imagination. Humour is practically non-existent unless it is understood; and, as a more recent humourist has whimsically insisted, there may be here a kind of division of labour, the humour being lodged in one mind and the comprehension of it in another. It is so with Dickens. He sympathises, appreciates, interprets, and thus in part creates. He frequently makes the fun by his own keen sense of it.